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Document and Entity Information Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2017	Nov. 30, 2017
Class of Stock [Line Items]
Entity Registrant Name	Bandwidth Inc.
Entity Central Index Key	0001514416
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Document Type	10-Q
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q3
Amendment Flag	false
Common Class A
Class of Stock [Line Items]
Entity Common Stock, Shares Outstanding		4,197,831
Common Class B
Class of Stock [Line Items]
Entity Common Stock, Shares Outstanding		13,423,489

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 5,366	$ 6,788
Accounts receivable, net of allowance for doubtful accounts	18,702	16,838
Prepaid expenses and other current assets	6,157	4,416
Total current assets	30,225	28,042
Property and equipment, net	12,389	11,181
Intangible assets, net	7,853	8,482
Deferred costs, non-current	4,903	1,696
Other long-term assets	1,069	1,011
Goodwill	6,867	6,867
Deferred tax asset	9,244	12,694
Total assets	72,550	69,973
Current liabilities:
Accounts payable	2,518	4,688
Accrued expenses and other current liabilities	15,783	14,649
Current portion of deferred revenue and advanced billings	4,710	4,032
Line of credit, current portion	0	5,000
Current portion of long-term debt	2,849	2,100
Total current liabilities	25,860	30,469
Other liabilities	1,431	611
Deferred revenue, net of current portion	2,439	1,711
Long-term debt, net of current portion	35,501	37,738
Total liabilities	65,231	70,529
Redeemable convertible preferred stock	21,818	21,818
Commitments and contingencies
Stockholders’ deficit:
Class A and Class B common stock	12	12
Additional paid-in capital	10,661	9,356
Accumulated deficit	(25,172)	(31,742)
Total stockholders’ deficit	(14,499)	(22,374)
Total liabilities, redeemable convertible preferred stock and stockholders’ deficit	$ 72,550	$ 69,973

Condensed Consolidated Statements of Operations and Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
Revenue	$ 41,338	$ 38,603	$ 120,489	$ 113,373
Cost of revenue	22,571	21,514	66,431	64,177
Gross profit	18,767	17,089	54,058	49,196
Operating expenses:
Research and development	2,771	2,390	7,862	6,157
Sales and marketing	3,128	2,418	8,099	6,876
General and administrative	9,797	7,899	25,691	23,571
Total operating expenses	15,696	12,707	41,652	36,604
Operating income	3,071	4,382	12,406	12,592
Other expense, net	(538)	(229)	(1,950)	(597)
Income from continuing operations before income taxes	2,533	4,153	10,456	11,995
Income tax provision	(899)	(137)	(3,886)	(406)
Income from continuing operations	1,634	4,016	6,570	11,589
Loss from discontinued operations, net of income taxes	0	(728)	0	(3,739)
Net income	1,634	3,288	6,570	7,850
Total comprehensive income, net of income tax	1,634	3,288	6,570	7,850
Less: income allocated to participating securities	213	531	858	1,533
Income from continuing operations attributable to common stockholders	$ 1,421	$ 3,485	$ 5,712	$ 10,056
Income from continuing operations per share:
Basic (in usd per share)	$ 0.12	$ 0.30	$ 0.48	$ 0.86
Diluted (in usd per share)	$ 0.11	$ 0.27	$ 0.42	$ 0.78
Less: income allocated to participating securities	$ 213	$ 435	$ 858	$ 1,038
Net income attributable to common stockholders	$ 1,421	$ 2,853	$ 5,712	$ 6,812
Net income per share:
Basic (in usd per share)	$ 0.12	$ 0.25	$ 0.48	$ 0.59
Diluted (in usd per share)	$ 0.11	$ 0.22	$ 0.42	$ 0.53
Weighted average number of common shares outstanding:
Basic (in shares)	11,828,657	11,600,189	11,814,045	11,643,664
Diluted (in shares)	13,252,737	12,810,379	13,487,649	12,828,894

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Operating activities
Net income	$ 6,570	$ 7,850
Loss from discontinued operations, net of income taxes	0	3,739
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	4,272	4,768
Amortization of debt issuance costs	96	27
Stock-based compensation	1,102	1,099
Change in fair value of shareholders’ anti-dilutive arrangement	689	0
Deferred taxes	3,450	253
Loss on disposal of property and equipment	55	11
Changes in operating assets and liabilities:
Accounts receivable	(1,864)	(3,483)
Prepaid expenses and other assets	(1,470)	(1,421)
Deferred costs	(3,556)	(671)
Accounts payable	(2,170)	1,087
Accrued expenses and other liabilities	1,267	(1,598)
Deferred revenue and advance billings	1,405	1,066
Net cash provided by operating activities from continuing operations	9,846	12,727
Net cash used in operating activities from discontinued operations	0	(7,613)
Net cash provided by operating activities	9,846	5,114
Investing activities
Purchase of property and equipment	(2,323)	(2,688)
Capitalized software development costs	(2,586)	(1,537)
Net cash used in investing activities from continuing operations	(4,909)	(4,225)
Net cash used in investing activities from discontinued operations	0	(1,005)
Net cash used in investing activities	(4,909)	(5,230)
Financing activities
Borrowings on line of credit	4,000	40,200
Repayments on line of credit	(9,000)	(45,200)
Payments on capital leases	(49)	(81)
Repayments on term loan	(1,500)	0
Payment of debt issuance costs	0	(13)
Proceeds from issuances of common stock	174	932
Decrease in restricted cash	16	38
Net cash used in financing activities from continuing operations	(6,359)	(4,124)
Net decrease in cash and cash equivalents	(1,422)	(4,240)
Cash and cash equivalents, beginning of period	6,788	10,059
Cash and cash equivalents, end of period	5,366	5,819
Supplemental disclosure of cash flow information
Cash paid during the year for interest	1,346	571
Cash paid for taxes	691	159
Supplemental disclosure of noncash financing activities
Acquisition of equipment through capital leases	$ 0	$ 132

Organization and Description of Business	9 Months Ended
Organization and Description of Business	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Description of Business	1. Organization and Description of Business Bandwidth Inc. (together with its subsidiaries, “Bandwidth” or the “Company”) was founded in July 2000 and incorporated in Delaware on March 29, 2001. The Company’s headquarters are located in Raleigh, North Carolina. The Company is a cloud-based, software-powered communications platform-as-a-service (“CPaaS”) provider that enables enterprises to create, scale and operate voice or text communications services across any mobile application or connected device or enterprises. The Company has two operating and reportable segments, CPaaS and Other. CPaaS revenue is derived from usage and monthly services fees charged for usage of Voice, Messaging, 911 and Phone Numbers solutions through the Company’s proprietary CPaaS software application programming interfaces. Other revenue consists of fees charged for services provided such as: SIP trunking, data resale, and a hosted Voice-over Internet Protocol (“VoIP”). The Other segment also includes revenue from traffic generated by other carriers (“CABS”), SMS registrations fees and other miscellaneous product lines. Initial Public Offering On November 9, 2017, the Company's Registration Statement on Form S-1 relating to the initial public offering (“IPO”) of its Class A common stock was declared effective by the SEC. Immediately prior to the closing of the initial public offering, the Company’s certificate of incorporation was amended such that (i) each share of the Company’s then-outstanding Class A voting common stock (“Old Class A common stock”) was reclassified as one share of Class B common stock (“New Class B common stock”), which has ten votes per share, (ii) each share of the Company’s then-outstanding Class B non-voting common stock (“Old Class B common stock”) was reclassified as one share of Class A common stock ("New Class A common stock"), which has one vote per share and (iii) options and warrants exercisable into the Company’s Old Class A common stock and Old Class B common stock became exercisable into New Class B common stock and New Class A common stock, respectively. In addition, immediately prior to pricing of the IPO, all shares of the Company’s then-outstanding convertible preferred stock were converted into New Class B common stock. In connection with the Company’s IPO 4,000,000 shares of the Company's New Class A common stock were sold at an initial public offering price of $20.00 per share for proceeds of approximately $74,400, net of underwriting discounts and commissions.

Summary of Significant Accounting Policies	9 Months Ended
Summary of Significant Accounting Policies	Sep. 30, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”) and applicable rules and regulations of the SEC regarding interim financial reporting. Certain information and note disclosures normally included in the financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. Therefore, these condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes included in the final prospectus filed with the SEC pursuant to Rule 424(b) under the Securities Act on November 13, 2017 (the “Prospectus”). The Company had no components of other comprehensive income during any of the periods presented, and as such, a separate consolidated statement of comprehensive income is not presented. The condensed consolidated balance sheet as of December 31, 2016, included herein, was derived from the audited financial statements as of that date, but does not include all disclosures including certain notes required by GAAP on an annual reporting basis. In the opinion of management, the accompanying unaudited condensed consolidated financial statements reflect all normal recurring adjustments necessary to present fairly the financial position, results of operations, comprehensive income and cash flows for the interim periods, but are not necessarily indicative of the results of operations to be anticipated for the full year 2017 or any future period. Principles of Consolidation The condensed consolidated financial statements include the accounts of Bandwidth Inc. and its wholly owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation. Use of Estimates The preparation of the Company’s consolidated financial statements in conformity with GAAP requires the Company to make estimates and judgments that affect the amounts reported in these financial statements and accompanying notes. Although the Company believes the estimates it uses are reasonable, due to the inherent uncertainty involved in making these estimates, actual results reported in future periods could differ from those estimates. These estimates in the condensed consolidated financial statements include, but are not limited to, allowance for doubtful accounts, recoverability of long-lived and intangible assets, customer relationship period, valuation allowances on tax assets, certain accrued expenses, and contingencies. Concentration of Credit Risk Financial instruments that are exposed to concentration of credit risk consist primarily of cash and cash equivalents and trade accounts receivable. Cash deposits may be in excess of insured limits. The Company believes that the financial institutions that hold its cash deposits are financially sound and, accordingly, minimal credit risk exists with respect to these balances. With regard to customers, credit evaluation and account monitoring procedures are used to minimize the risk of loss. The Company believes that no additional credit risk beyond amounts provided for by the allowance for doubtful accounts are inherent in accounts receivable. No individual customer represented more than 10 percent of accounts receivable as of December 31, 2016 and September 30, 2017. For the three and nine months ended September 30, 2016 and 2017, no individual customer represented more than 10 percent of the Company’s total revenue. Significant Accounting Policies There have been no changes to our significant accounting policies described in the Prospectus. Recent Accounting Pronouncements Not Yet Adopted In May 2017, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2017-09, Compensation-Stock Compensation (Topic 718), Scope of Modification Accounting, which amends the scope of modification accounting for share-based payment arrangements. The ASU provides guidance on the types of changes to terms or conditions of share-based payment awards to which an entity would be required to apply modification accounting under ASC 718, Compensation-Stock Compensation. ASU 2017-09 is effective for fiscal years and interim periods within those years beginning after December 15, 2017, and early adoption is permitted. The Company is evaluating the impact of this guidance on its consolidated financial statements and related disclosures. In January 2017, the FASB issued ASU 2017-04, Simplifying the Test for Goodwill Impairment, which simplifies the accounting for goodwill impairment. The ASU requires impairment charges to be based on the first step in today’s two-step impairment test under Accounting Standards Codification (“ASC”) 350. ASU 2017-04 is effective for annual and interim impairment tests performed in periods beginning after December 15, 2021, and early adoption is permitted. The Company is evaluating the impact of this guidance on its consolidated financial statements and related disclosures. In January 2017, the FASB issued ASU 2017-01, Business Combinations (Topic 805) Clarifying the Definition of a Business, which amends the guidance of FASB Accounting Standards Codification Topic 805, “Business Combinations”, adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions or disposals of assets or businesses. The definition of a business affects many areas of accounting including acquisitions, disposals, goodwill, and consolidation. This guidance is effective for annual and interim periods beginning after December 15, 2017, and early adoption is permitted under certain circumstances. The adoption of this standard is dependent upon future transactions. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230), Classification of Certain Cash Receipts and Cash Payments, which clarifies how entities should classify certain cash receipts and cash payments on the statement of cash flows. The guidance also clarifies how the predominance principle should be applied when cash receipts and cash payments have aspects of more than one class of cash flows. ASU 2016-15 is effective for fiscal years beginning after December 15, 2018, and interim periods within fiscal years beginning after December 15, 2019, and early adoption is permitted. Entities will have to apply the guidance retrospectively, but if it is impracticable to do so for an issue, the amendments related to that issue would be applied prospectively. The Company is evaluating the impact of this guidance on its consolidated financial statements and related disclosures. In February 2016, the FASB issued ASU 2016-02, Leases. The standard will affect all entities that lease assets and will require lessees to recognize a lease liability and a right-of-use asset for all leases (except for short- term leases that have a duration of less than one year) as of the date on which the lessor makes the underlying asset available to the lessee. For lessors, accounting for leases is substantially the same as in prior periods. ASU 2016-02 is effective for fiscal years beginning after December 15, 2019, and interim periods within annual periods beginning after December 15, 2020, and early adoption is permitted. For leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements, lessees and lessors must apply a modified retrospective transition approach. While the Company expects the adoption of this standard to result in an increase to the reported assets and liabilities, it has not yet determined the full impact that the adoption of this standard will have on its financial statements and related disclosures. In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers. This new guidance will replace most existing. GAAP guidance on this topic. The new revenue recognition standard provides a unified model to determine when and how revenue is recognized. The core principle is that a company should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration for which the entity expects to be entitled in exchange for those goods or services. In August 2015, the FASB issued ASU 2015-14, Revenue from Contracts with Customers: Deferral of the effective date, which deferred by one year the effective date for the new revenue reporting standard for entities reporting under GAAP. In accordance with the deferral, this guidance will be effective beginning January 1, 2019. This guidance can be applied either retrospectively to each period presented or as a cumulative-effect adjustment as of the date of adoption. Early adoption is permitted beginning January 1, 2017. In December 2016, the FASB issued ASU 2016-20, Revenue from Contracts with Customers, Technical Corrections and Improvements to Topic 606, which made twelve additional technical corrections and improvements to the new revenue standard. In March 2016, the FASB issued ASU 2016-08, Revenue from Contracts with Customers, Principal versus Agent Considerations (Reporting Revenue Gross versus Net) clarifying the implementation guidance on principal versus agent considerations. Specifically, an entity is required to determine whether the nature of a promise is to provide the specified good or service itself (that is, the entity is a principal) or to arrange for the good or service to be provided to the customer by the other party (that is, the entity is an agent). The determination influences the timing and amount of revenue recognition. In April 2016, the FASB issued ASU 2016-10, Revenue from Contracts with Customers, Identifying Performance Obligations and Licensing, clarifying the implementation guidance on identifying performance obligations and licensing. Specifically, the amendments reduce the cost and complexity of identifying promised goods or services and improve the guidance for determining whether promises are separately identifiable. The amendments also provide implementation guidance on accounting for an entity’s promise to grant a license. In May 2016, the FASB issued ASU 2016-12, Revenue from Contracts with Customers, Narrow-Scope Improvements and Practical Expedients, clarifying guidance on assessing collectability, presentation of sales taxes, noncash consideration, completed contracts and contract modifications. The effective date and transition requirements for ASU 2016-20, ASU 2016-08 and ASU 2016-10 are the same as the effective date and transition requirements for ASU 2014-09. The Company is still assessing all potential impacts of the new standard on its consolidated financial statements. Given the comprehensive nature of the standard, the Company has already taken steps to begin assessing the impact on its consolidated financial results. It has completed a preliminary diagnostic, in order to highlight potential differences between current accounting policies and the new standard, and has begun drafting memos to document its accounting positions. Additionally, the Company engaged a third-party service provider to assist in its evaluation of customer contracts and to identify the attributes that could result in a different accounting treatment under ASU 2014-09. From an information technology perspective, the Company has identified a new technology solution which meets its business requirements and will be implemented to comply with ASC 2014-09. The Company has not reached a conclusion as to whether the quantitative effect of the adoption of the new standard on its revenue streams will be material. It will continue to monitor and assess the impact of the changes of the new standard and the related interpretations of its application as they become available.

Discontinued Operations

9 Months Ended

Sep. 30, 2017

Discontinued Operations and Disposal Groups [Abstract]

Discontinued Operations

3. Discontinued Operations

On April 20, 2015, the Company created a wholly owned subsidiary, Republic Wireless, Inc. (“Republic”), which was incorporated in Delaware. On November 30, 2016, the Company completed a pro-rata distribution of the common stock of Republic to its stockholders of record as of the close of business (the “Spin-Off”). Each of its stockholders received one share of Republic common stock for each share of Bandwidth common or redeemable convertible preferred stock held as of the close of business on November 30, 2016. Accordingly, the results of operations, financial condition and cash flows of Republic have been presented as discontinued operations for all periods presented in the accompanying consolidated financial statements.

The table below provides the operating results of the discontinued operations for the three and nine months ended September 30, 2016:



	Three Months Ended September 30, 2016			Nine Months Ended September 30, 2016
Revenue	$	25,919		$	68,164
Direct costs of network services and equipment	(19,335		)	(50,823		)
Operating expense	(7,072		)	(20,312		)
Depreciation and interest	(240		)	(768		)
Loss from discontinued operations	$	(728	)	$	(3,739	)

Fair Value of Financial Instruments

9 Months Ended

Sep. 30, 2017

Fair Value Disclosures [Abstract]

Fair Value of Financial Instruments

4. Fair Value of Financial Instruments

The carrying amounts of cash and cash equivalents, accounts receivable, accounts payable and accrued expenses approximate fair value as of December 31, 2016 and September 30, 2017 because of the relatively short duration of these instruments. The carrying value of long-term debt approximates fair value given the interest rates are based on market rates.

The Company evaluated its financial assets and liabilities subject to fair value measurements on a recurring basis to determine the appropriate level in which to classify them for each reporting period. The following table summarizes the assets and liabilities measured at fair value as of December 31, 2016 and September 30, 2017:



	Fair Value Measurements on a Recurring Basis December 31, 2016
	Level 1		Level 2		Level 3			Total
Money Market Account	$	63	$	—	$	—		$	63
Shareholders’ anti-dilutive arrangement	—		—		(184		)	(184		)



	Fair Value Measurements on a Recurring Basis September 30, 2017
	Level 1		Level 2		Level 3			Total
Money Market Account	$	64	$	—	$	—		$	64
Shareholders’ anti-dilutive arrangement	—		—		(873		)	(873		)

There were no transfers between Levels 1, 2 or 3 during the year ended December 31, 2016 or the nine months ended September 30, 2017.

The money market account is included in cash and cash equivalents in the consolidated balance sheets as of December 31, 2016 and September 30, 2017.

On February 22, 2011, the Company entered into an agreement with the Principal Non-Founder Stockholders ("Principal Stockholders"). Under the terms of the agreement, the Principal Stockholders received the right (“shareholders' anti-dilutive arrangement”) to purchase a pro-rata number of shares based on their ownership percentage of outstanding shares, when certain option holders exercise his or her stock option. The price at which the Principal Stockholders may purchase their pro-rata shares matches the exercise price of the option exercised. The Principal Stockholders have 90 days from the date of receipt of notice to inform the Company of their intention to purchase stock under the terms of the agreement. On a quarterly basis, the Company adjusts this liability to fair value.

The agreement terminates by one of the following events:


•	closing of a “Qualified Public Offering,” which is defined as one resulting in aggregate net proceeds to the Company equal to or greater than $20 million, or


•	a “true sale” as defined in the Investors’ Rights Agreement.

Upon termination of the agreement, this liability would terminate.

The shareholders’ anti-dilutive arrangement is included in other liabilities in the consolidated balance sheets as of December 31, 2016 and September 30, 2017. The change in fair value of the Level 3 liability resulted in $136 and $689 of additional expense for the three and nine months ended September 30, 2017, respectively, which is recorded in other expense in the condensed consolidated statements of operations and comprehensive income.

The fair value of the shareholders’ anti-dilutive arrangement is estimated using the Black-Scholes-Merton option pricing model. The significant unobservable inputs used in the fair value measurement of the shareholders’ anti-dilutive arrangement are the fair value of the Company’s stock and the expected term of the options. The expected term is calculated as a weighted average of the estimated time to IPO as of the measurement date and the historical average term of options subject to the agreement which were vested and expired or were exercised. Volatility is based on the historical volatility of certain public entities that are similar to the Company as the Company does not have sufficient historical transactions of its own shares on which to base expected volatility. Significant increases (decreases) in the fair value of the Company’s stock price would result in a significantly larger (smaller) fair value liability measurement. Significant increases (decreases) in the expected term would result in a larger (smaller) fair value liability measurement.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Financial Statement Components

9 Months Ended

Sep. 30, 2017

Financial Statement Components [Abstract]

Financial Statement Components

5. Financial Statement Components

Accounts receivable, net of allowance for doubtful accounts consisted of the following:



	December 31, 2016			September 30, 2017
Trade accounts receivable	$	31,734		$	40,351
Unbilled accounts receivable	7,368			7,859
Allowance for doubtful accounts	(22,571		)	(30,040		)
Other accounts receivable	307			532
Total accounts receivable, net	$	16,838		$	18,702

Accounts receivable are stated at realizable value, net of an allowance for doubtful accounts. The allowance for doubtful accounts is based on management’s assessment of the collectability of its accounts receivable. The Company regularly reviews the composition of the accounts receivable aging, historical bad debts, changes in payment patterns, customer creditworthiness and current economic trends. If the financial condition of customers were to deteriorate, resulting in their inability to make required payments, additional provisions for doubtful accounts would be required and would increase bad debt expense. Management has evaluated the collectability of trade accounts receivable and determined that allowances of approximately $22,571 and $30,040 for uncollectible accounts and customer balances that are disputed were required as of December 31, 2016 and September 30, 2017, respectively. The allowance for doubtful accounts primarily relates to billings for CABS services where collectability was not probable. A roll forward of the components of the allowance for doubtful accounts for the three and nine months ended September 30, 2016 and 2017 are as follows:



	Three Months Ended September 30,						Nine Months Ended September 30,
Allowance for doubtful accounts:	2016			2017			2016			2017
Balance, beginning of period	$	182		$	112		$	238		$	255
Charged to bad debt expense	(87		)	83			45			95
Deductions(1)	(25		)	(19		)	(213		)	(174		)
Balance, end of period	$	70		$	176		$	70		$	176

________________________

(1) Write off of uncollectible accounts after all collection efforts have been exhausted.



	Three Months Ended September 30,						Nine Months Ended September 30,
Allowance for CABS revenue:	2016			2017			2016			2017
Balance, beginning of period	$	15,641		$	27,401		$	12,318		$	22,316
Billings deemed not probable of collection(1)	5,119			2,485			8,466			7,613
Deductions(2)	(1		)	(22		)	(25		)	(65		)
Balance, end of period	$	20,759		$	29,864		$	20,759		$	29,864

________________________

(1) Represents amounts billed but where collectibility is not probable based on customers collection experience. Amounts were charged to a contra-revenue account.

(2) Write off of uncollectible accounts after all collection efforts have been exhausted.



	Three Months Ended September 30,				Nine Months Ended September 30,
CABS revenue:	2016		2017		2016		2017
Billed	$	7,246	$	4,992	$	15,094	$	14,501
Revenue recognized	2,127		2,507		6,628		6,888
Billings deemed not probable of collection(1)	$	5,119	$	2,485	$	8,466	$	7,613

________________________

(1) Represents amounts billed but where collectibility is not probable based on customers collection experience. Amounts were charged to a contra-revenue account.

Accrued expenses and other current liabilities consisted of the following:



	December 31, 2016		September 30, 2017
Accrued expense	$	6,853	$	8,319
Accrued compensation and benefits(1)	4,373		4,656
Accrued sales, use, and telecom related taxes	2,769		2,325
Other accrued expenses	654		483
Total accrued expenses	$	14,649	$	15,783

________________________

(1) On September 1, 2017, the Company reached a separation agreement with one of its executives. The agreement resulted in a severance liability of approximately $660 as of September 30, 2017.

Property and Equipment

9 Months Ended

Sep. 30, 2017

Property, Plant and Equipment [Abstract]

Property and Equipment

6. Property and Equipment

Property and equipment, net consisted of the following:



	December 31, 2016			September 30, 2017
Furniture and fixtures	$	680		$	680
Computer and office equipment	7,539			7,525
Telecommunications equipment	13,718			16,815
Leasehold improvements	453			453
Software development costs	13,677			15,198
Automobile	10			10
Total cost	36,077			40,681
Less—accumulated depreciation	(24,896		)	(28,292		)
Total property and equipment, net	$	11,181		$	12,389

The Company capitalized $612 and $1,537 of software development costs in the three and nine months ended September 30, 2016, respectively, and $988 and $2,586 in the three and nine months ended September 30, 2017, respectively.

Amortization of capitalized software development costs was $929 and $2,766 for the three and nine months ended September 30, 2016, respectively, and $524 and $1,659 for the three and nine months ended September 30, 2017, respectively.

The Company recognized depreciation expense, which includes amortization of capitalized software development costs, as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
	2016		2017		2016		2017
Cost of revenue	$	1,155	$	1,161	$	3,514	$	3,245
Research and development	15		29		64		51
Sales and marketing	6		6		15		20
General and administrative	149		45		506		327
Total depreciation expense	$	1,325	$	1,241	$	4,099	$	3,643

Intangible Assets

9 Months Ended

Sep. 30, 2017

Goodwill and Intangible Assets Disclosure [Abstract]

Intangible Assets

7. Intangible Assets

Intangible assets consisted of the following as of December 31, 2016:



	Gross Amount		Accumulated Amortization			Net Carrying Value		Amortization Period
								(Years)
Customer relationships	$	10,396	$	(3,032	)	$	7,364	20
Domain name and related trademarks	2,678		(2,324		)	354		3–7
Licenses, amortizable	341		(341		)	—		2
Non-compete agreements	139		(139		)	—		2–5
Developed technology	775		(775		)	—		3
Licenses, indefinite lived	764		—			764		Indefinite
Total intangible assets, net	$	15,093	$	(6,611	)	$	8,482

Intangible assets consisted of the following as of September 30, 2017:



	Gross Amount		Accumulated Amortization			Net Carrying Value		Amortization Period
								(Years)
Customer relationships	$	10,396	$	(3,422	)	$	6,974	20
Domain name and related trademarks	2,678		(2,563		)	115		3–7
Licenses, amortizable	341		(341		)	—		2
Non-compete agreements	139		(139		)	—		2–5
Developed technology	775		(775		)	—		3
Licenses, indefinite lived	764		—			764		Indefinite
Total intangible assets, net	$	15,093	$	(7,240	)	$	7,853

Amortization expense for definite lived intangible assets was $222 and $669 in the three and nine months ended September 30, 2016, respectively, and $210 and $629 in the three and nine months ended September 30, 2017, respectively. The weighted average amortization period for all definite lived intangible assets is 19 years.

Future estimated amortization expense subsequent to September 30, 2017 is as follows:



	Amount
2017 (remaining three months)	$	209
2018	555
2019	520
2020	520
2021	520
Thereafter	4,765
	$	7,089

Debt

9 Months Ended

Sep. 30, 2017

Debt Disclosure [Abstract]

Debt

8. Debt

As of December 31, 2016 and September 30, 2017, the Company had $40,000 and $38,500, respectively, outstanding on the term loan and $5,000 and $0, respectively, on the revolving loan and was in compliance with all financial and non-financial covenants for all periods presented. The available borrowing under the Credit and Security Agreement was $25,000 as of September 30, 2017. Beginning on March 31, 2017, the term loan is payable in consecutive equal quarterly installments with the balance payable in full on the term loan maturity date (November 3, 2021). Future payments under the term loan subsequent to September 30, 2017 are as follows:



	Amount
2017 (remaining three months)	$	500
2018	3,000
2019	3,000
2020	4,000
2021	28,000
	$	38,500

As of December 31, 2016 and September 30, 2017, the outstanding unamortized loan fees for the revolving loan were $199 and $163, respectively, and were included in other long-term assets. As of December 31, 2016 and September 30, 2017, unamortized loan fees for the term loan were $326 and $266, respectively, which are netted against long-term debt.

Capital Leases

The Company leases various equipment under leases accounted for as capital leases with expiration dates ranging from March 2016 through October 2018. As of December 31, 2016, cost and accumulated depreciation of the assets under capital leases recorded by the Company were $1,951 and $1,807, respectively. As of September 30, 2017, cost and accumulated depreciation of the assets under capital leases recorded by the Company were $1,951 and $1,865, respectively.

Remaining payments due on the Company’s capital lease obligations as of September 30, 2017, are as follows:



	Amount
2017	$	25
2018	91
Less amount representing interest	—
	116
Less current maturities	99
	$	17

Segment and Geographic Information

9 Months Ended

Sep. 30, 2017

Segment Reporting [Abstract]

Segment and Geographic Information

9. Segment and Geographic Information

The Company has two reportable segments CPaaS and Other. Segments are evaluated based on revenue and gross profit. The Company does not allocate operating expenses, interest expense or income tax expense to its segments. Accordingly, the Company does not report such information. Additionally, the Chief Operating Decision Maker ("CODM") does not evaluate the Company’s operating segments using discrete asset information. The segments share the majority of the Company’s assets. Therefore, no segment asset information is reported.



	Three Months Ended September 30,				Nine Months Ended September 30,
	2016		2017		2016		2017
CPaaS
Revenue	$	30,249	$	33,397	$	86,900	$	96,591
Cost of revenue	18,197		19,247		53,576		56,394
Gross profit	$	12,052	$	14,150	$	33,324	$	40,197
Other
Revenue	$	8,354	$	7,941	$	26,473	$	23,898
Cost of revenue	3,317		3,324		10,601		10,037
Gross profit	$	5,037	$	4,617	$	15,872	$	13,861
Consolidated
Revenue	$	38,603	$	41,338	$	113,373	$	120,489
Cost of revenue	21,514		22,571		64,177		66,431
Gross profit	$	17,089	$	18,767	$	49,196	$	54,058

All assets were held in the United States as of December 31, 2016 and September 30, 2017.

The Company generates its revenue primarily in the United States. Revenue by geographical area is detailed in the table below (which is determined based on the customer billing address):



	Three Months Ended September 30,				Nine Months Ended September 30,
	2016		2017		2016		2017
United States	$	38,408	$	41,188	$	113,027	$	120,090
International	195		150		346		399
Total	$	38,603	$	41,338	$	113,373	$	120,489

Redeemable Convertible Preferred Stock and Stockholder's Deficit Redeemable Convertible Preferred Stock and Stockholder's Deficit (Notes)	9 Months Ended
	Sep. 30, 2017
Equity [Abstract]
Redeemable Convertible Preferred Stock and Stockholder's Deficit	10. Redeemable Convertible Preferred Stock and Stockholders’ Deficit On October 19, 2017, the Company’s Board of Directors approved, and on October 23, 2017 the Company effected, a 2.50-to-1 split of its common stock. In connection with the common stock split, each share of outstanding common stock, option to purchase common stock and warrant to purchase common stock was increased to 2.50 shares of common stock and the exercise price of each outstanding option or warrant to purchase common stock was proportionately decreased. The stock split has been reflected retrospectively in these condensed consolidated financial statements. In connection with the stock split, the conversion ratio of each share of outstanding redeemable convertible preferred stock was also adjusted such that each share of outstanding redeemable convertible preferred stock converts into 2.50 shares of Old Class A common stock after the 2.50-to-1 split. Redeemable Convertible Preferred Stock As of December 31, 2016 and September 30, 2017, 710,000 shares of redeemable convertible preferred stock ("Series A preferred stock") were issued and outstanding. The holders of Series A preferred stock shall be entitled to cast the number of votes equal to the number of whole shares of common stock into which the shares of Series A preferred stock are convertible as of the record date for determining stockholders entitled to vote on such matter. Holders of Series A preferred stock shall vote together with the holders of common stock as a single class. Each share of Series A preferred stock shall be convertible, at the option of the shareholder, into such number of fully paid and non-assessable shares of common stock as is determined by dividing the Series A original issue price by the Series A conversion price in effect at the time of the conversion. The Series A conversion price was initially equal to $30.8358 and is subject to adjustment related to dilutive transactions. As a result of the stock split referred to above, the conversion ratio of each share of outstanding preferred stock also was adjusted subsequent to September 30, 2017, such that each share of outstanding preferred stock converts into 2.50 shares of Old Class A common stock at a conversion price of $12.3343. Common Stock As of December 31, 2016 and September 30, 2017, the Company had two classes of common stock: (1) Old Class A common stock and (2) Old Class B common stock. The Old Class A common stock had one vote per share and the Old Class B common stock was non-voting. As of December 31, 2016 and September 30, 2017, 11,779,975 and 11,811,480 shares of Old Class A common stock were issued and outstanding at $0.001 par value per share, respectively. As of December 31, 2016 and September 30, 2017, 18,590 and 34,840 shares of Old Class B common stock were issued and outstanding at $0.001 par value per share, respectively. Pursuant to the Company’s second amended and restated certificate of incorporation and the effectiveness of its second amended and restated bylaws, which were effective on November 9, 2017 (i) each share of Old Class A common stock, including those shares of Old Class A common stock issued upon the conversion of then-outstanding Series A preferred stock, was reclassified as one share of New Class B common stock, with each share of New Class B common stock having ten votes per share, (ii) each share of Old Class B common stock was reclassified as one share of New Class A common stock, with each share of New Class A common stock having one vote per share. Subsequent to the effectiveness of the Company’s second amended and restated certificate of incorporation, the Company’s common stock consists of 120,000,000 authorized shares, par value $0.001 per share, of which the authorized New Class A common stock will consist of 100,000,000 shares and the authorized New Class B common stock will consist of 20,000,000 shares. On November 9, 2017, the Series A preferred stock was converted at the option of the holder into 1,775,000 shares of New Class B common stock. Stock Purchase Warrants As of December 31, 2016 and September 30, 2017, a total of 64,691 shares of common stock were reserved for the issuance of stock purchase warrants.

Stock Based Compensation

9 Months Ended

Sep. 30, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock Based Compensation

11. Stock Based Compensation

2001 and 2010 Stock Option Plans

During 2001, the Company adopted the Bandwidth Inc. Stock Option Plan (the 2001 Plan). As of July 26, 2010, the Company adopted the 2010 Equity Compensation Plan (the 2010 Plan). On August 24, 2017, the 2010 Plan was amended to provide for a total of 3,466,275 shares of common stock reserved for issuance under the 2010 Plan.

Eligible plan participants include employees, directors and consultants. The 2001 Plan and the 2010 Plan each permit the granting of incentive stock options and non-qualified stock options.

The terms of the stock option grants are determined by the Company’s Board of Directors. The Company’s stock options vest based on terms in the stock option agreements, which is generally over four years. The stock options have a contractual life of ten years.

The fair value of options granted is estimated on the date of grant using the Black-Scholes-Merton option pricing model based on the assumptions in the table below:



	Three Months Ended September 30,		Nine Months Ended September 30,
	2016	2017	2016	2017
Expected dividend yield	0%	0%	0%	0%
Expected stock price volatility	44%	47%-49%	44%	44%-49%
Average risk-free interest rate	1.3%	1.9%	1.3%–1.6%	1.9%–2.3%
Expected life	6.2 years	6.2 years	6.2 years	6.2 years
Fair value of common stock	$9.57	$18.40-$20.83	$9.57	$9.60-$20.83

The Company uses the simplified method for purposes of determining the expected life of the options. The risk-free interest rate is based on the U.S. Treasury rates at the date of grant with maturity dates approximately equal to the expected life at the grant date. Volatility is based on the historical volatility of certain public entities that are similar to the Company, as the Company does not have sufficient historical transactions of its own shares on which to base expected volatility. The Company historically has not issued any dividends and does not expect to in the future.

The following summarizes the stock option activity for the periods presented:



	Number of Options Outstanding		Weighted- Average Exercise Price (per share)		Weighted- Average Remaining Contract Life (in years)	Aggregate Intrinsic value (in thousands)
Balance, December 31, 2016	3,582,241		$	6.54	5.12	$	11,049
Grants	179,922		13.79
Exercised	(58,162	)	5.27			445
Forfeited or cancelled	(41,115	)	9.48
Balance, September 30, 2017	3,662,886		$	6.88	4.63	$	51,292
Options vested and exercisable at September 30, 2017	3,159,450		$	6.23	4.01	$	46,326
Options vested and expected to vest as of September 30, 2017	3,640,526		$	6.85	4.60	$	51,092

Aggregate intrinsic value represents the total pre-tax intrinsic value, which is computed based on the difference between the option exercise price and the estimated fair value of the Company’s common stock. This amount changes based on the fair value of the Company’s stock.

The weighted average grant-date fair value of stock options granted was $4.03 and $4.04 for the three and nine months ended September 30, 2016, and $9.45 and $7.48 for the three and nine months ended September 30, 2017 respectively.

The total estimated grant date fair value of options vested was $188 and $1,900 for the three and nine months ended September 30, 2016, respectively, and $443 and $1,070 for the three and nine months ended September 30, 2017, respectively.

The Company recognized total stock-based compensation expense in continuing operations as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
	2016		2017		2016		2017
Cost of revenue	$	17	$	17	$	45	$	57
Research and development	30		38		108		100
Sales and marketing	37		54		142		124
General and administrative(1)	161		503		804		821
Total	$	245	$	612	$	1,099	$	1,102

________________________

(1) On September 1, 2017, the Company reached a separation agreement with one of its executives. The agreement resulted in a modification of the former employee's 194,234 outstanding options to purchase common stock to accelerate the vesting period and extend the exercise period, which resulted in the recognition of $394 in additional stock compensation expense for the three months and nine months ended September 30, 2017.

The Company will recognize $2,191 of compensation cost in the future for stock-based employee compensation over the weighted-average of 2.7 years for stock options granted before September 30, 2017.

Commitments and Contingencies

9 Months Ended

Sep. 30, 2017

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

12. Commitments and Contingencies

Operating Leases

The Company leases office space under operating lease agreements that expire at various dates beginning in 2016 and extend through 2022 in several locations within the United States including its headquarters, which is located in Raleigh, NC. On September 26, 2016, the Company amended its operating lease agreement with one of its landlords. The 63-month lease, which begins on April 14, 2017, provides for an additional 40,657 square feet of office space as well as an extension of the termination date for the lease of approximately 128,200 square feet of office space. The leases contain escalation clauses and various landlord concessions including a tenant improvement allowance. The Company recognizes the total minimum lease payments on a straight-line basis over the term of the lease.

Future minimum lease payments required under operating leases as of September 30, 2017, for each of the years ending December 31, are as follows:



	Amount
2017	$	905
2018	3,631
2019	3,700
2020	3,838
2021	3,873
2022 and thereafter	2,018
	$	17,965

The Company incurred rent expense of $666 and $1,512 for the three and nine months ended September 30, 2016, respectively, and $1,034 and $2,414 for the three and nine months ended September 30, 2017, respectively, which is included in general and administrative expenses in the condensed consolidated statements of operations and comprehensive income.

In conjunction with the Spin-Off, the Company signed a Facilities Service Agreement with Republic in which the Company agreed to sub-lease 40,657 square feet of office space to Republic. The sub-lease is non-cancellable and extends to May 2022. The Company recorded a reduction of rent expense of $251 and $697 for the three and nine months ended September 30, 2017, respectively, which is included in general and administrative expenses in the condensed consolidated statements of operations and comprehensive income. No sub-lease payments were received for the nine months ended September 30, 2016 due to the Spin-Off having an effective date of November 30, 2016.

Future minimum sub-lease receipts as of September 30, 2017 for each of the years ending December 31, are as follows:



	Amount
2017	$	251
2018	1,020
2019	1,042
2020	1,065
2021	1,089
2022 and thereafter	594
	$	5,061

Contractual Obligations

On October 25, 2015, the Company entered into an agreement with a telecommunications service provider. The service agreement requires the Company to pay a monthly recurring charge beginning on January 1, 2016 associated with the services received. The service agreement is non-cancellable and contains annual minimum commitments of $1,200 to be fulfilled over five years or for as long as the Company continues to receive services from this vendor. In addition, the Company has other non-cancellable purchase obligations totaling $5,308 as of September 30, 2017, which consists primarily of network equipment to be received in less than one year.

Legal Matters

The Company is involved as a defendant in various lawsuits alleging that the Company failed to bill, collect and remit certain taxes and surcharges associated with the provision of 911 services pursuant to applicable laws in various jurisdictions. In August 2016, the Company received a Civil Investigative Demand from the Consumer Protection Division of the North Carolina Department of Justice, though no formal complaint has been filed in connection with that investigation. The North Carolina Department of Justice is investigating the billing, collection and remission of certain taxes and surcharges associated with 911 service pursuant to applicable laws of the State of North Carolina.

In April 2016, the Company filed counterclaims against MCI Communications Services, Inc. d/b/a Verizon Business and Verizon Select Services, Inc. (collectively, “Verizon”) in the United States District Court for the Northern District of Texas. The Company is pursuing collection of unpaid intercarrier compensation charges for providing switched access services related to the exchange of telecommunications traffic with Verizon entities across the United States. As of October 27, 2017, Verizon has asserted a counterclaim against the Company. The Company intends to contest such counterclaim vigorously. Verizon’s prior September 2014 complaint against the Company and other defendants regarding intercarrier compensation charges for providing switched access services related to the exchange of telecommunications traffic has been dismissed without prejudice, but remains subject to appeal.

While the results of these legal proceedings cannot be predicted with certainty, in the opinion of management, the ultimate resolution of these matters will not have a material adverse effect on the Company’s financial position or results of operations.

Employee Benefit Plan	9 Months Ended
Employee Benefit Plan	Sep. 30, 2017
Retirement Benefits [Abstract]
Employee Benefit Plan	13. Employee Benefit Plan The Company sponsors a defined contribution 401(k) plan which allows eligible employees to defer a portion of their compensation. The Company, at its discretion, may make matching contributions. The Company made matching contributions of $161 and $543 for the three and nine months ended September 30, 2016, respectively, and $181 and $596 for the three and nine months ended September 30, 2017, respectively.

Income Taxes	9 Months Ended
Income Taxes	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	14. Income Taxes At the end of each interim reporting period, the Company determines the income tax provision by using an estimate of the annual effective tax rate, adjusted for discrete items occurring in the quarter. The Company’s effective tax rate was 3.3% and 35.5% for the three months ended September 30, 2016 and September 30, 2017, respectively, compared to 3.4% and 37.2% for the nine months ended September 30, 2016 and September 30, 2017, respectively. The difference in tax rate for the three and nine months ended September 30, 2016, compared to the three and nine months ended September 30, 2017, is because the Company had a full valuation allowance for the nine months ended September 30, 2016. The effective income tax rate reflects the effect of federal and state income taxes and the permanent impacts of differences in book and tax accounting. The Company’s effective tax rate for this period is higher than the U.S. federal statutory rate of 34% primarily due to state taxes.

Related Parties	9 Months Ended
Related Parties	Sep. 30, 2017
Related Party Transactions [Abstract]
Related Parties	15. Related Parties In connection with the Spin-Off on November 30, 2016, the Company and Republic entered into certain agreements in order to govern the ongoing relationships between the two companies after the Spin-Off and to provide for an orderly transition. The agreements include a Transition Services Agreement, Facilities Sharing Agreement, Tax Sharing Agreement, and Master Services Agreement. The equity holders of Bandwidth are comprised of substantially the same individuals and entities that are the equity owners of Republic. The Company has determined the equity owners of Republic are related parties of Bandwidth. The Company has certain involvement with Republic via ongoing services arrangements, with these ongoing services arrangements creating a variable interest in Republic. The Company assessed the relationship with Republic under guidance for variable interest entities. Because investors in Republic have disproportionate voting rights, the Company concluded that Republic is a variable interest entity (“VIE”) but Bandwidth is not a primary beneficiary. The Company’s maximum exposure to loss relating to this variable interest entity is limited to amounts due under the service agreements between the Company and Republic. For the three and nine months ended September 30, 2017, the Company received net compensation under the Transition Services Agreement of $37 and $548, respectively. In addition, there was approximately $35 due from Republic under the Transition Services Agreement as of September 30, 2017, which was recorded within accounts receivable in the accompanying condensed consolidated balance sheet. For the three and nine months ended September 30, 2017, the Company received rental payments under the Facilities Sharing Agreement of $251 and $697, respectively, which is included in general and administrative expenses in the condensed consolidated statements of operations and comprehensive income. No amounts were due to the Company under the Facilities Sharing Agreement as of December 31, 2016 and September 30, 2017. There are no amounts outstanding or payable under the Tax Sharing Agreement as of December 31, 2016 and September 30, 2017. During the three and nine months ended September 30, 2017, the Company provided telecommunication service under the Master Services Agreement to Republic of $550 and $1,623, respectively. The Company recognized such amounts as revenue in the accompanying condensed consolidated statement of operations and comprehensive income. In addition, there was approximately $193 due from Republic under the Master Services Agreement as of September 30, 2017, which was recorded within accounts receivable in the accompanying condensed consolidated balance sheet.

Basic and Diluted Income (Loss) per Common Share

9 Months Ended

Sep. 30, 2017

Earnings Per Share [Abstract]

Basic and Diluted Income (Loss) per Common Share

16. Basic and Diluted Income (Loss) per Common Share

The Company uses the two-class method to compute net income per common share, because it has issued securities, other than common stock, that contractually entitle the holders to participate in dividends and earnings. These participating securities include the Company’s redeemable convertible preferred stock which have non-forfeitable rights to participate in any dividends declared on the Company’s common stock. The two-class method requires earnings for the period to be allocated between common stock and participating securities based upon their respective rights to receive distributed and undistributed earnings.

Under the two-class method, for periods with net income, basic net income per common share is computed by dividing the net income attributable to common stockholders by the weighted average number of shares of common stock outstanding during the period. Net income attributable to common stockholders is computed by subtracting from net income the portion of current period earnings that the participating securities would have been entitled to receive pursuant to their dividend rights had all of the period’s earnings been distributed. No such adjustment to earnings is made during periods with a net loss, as the holders of the participating securities have no obligation to fund losses.

Diluted net income (loss) per common share is computed under the two-class method by using the weighted average number of shares of common stock outstanding, plus, for periods with net income attributable to common stockholders, the potential dilutive effects of stock options and warrants. The Company analyzed the potential dilutive effect of any outstanding dilutive securities under the “if-converted” method and treasury-stock method when calculating diluted earnings per share, in which it is assumed that the outstanding participating securities convert into common stock at the beginning of the period or date of issuance, if later. The Company reports the more dilutive of the approaches (two-class or “if-converted”) as its diluted net income per share during the period.

The components of basic and diluted earnings per share, or EPS, are as follows:



	Three Months Ended September 30,					Nine Months Ended September 30,
	2016			2017		2016			2017
Income from Continuing Operations
Income from continuing operations	$	4,016		$	1,634	$	11,589		$	6,570
Less: income allocated to participating securities	531			213		1,533			858
Income from continuing operations attributable to common stockholders	$	3,485		$	1,421	$	10,056		$	5,712
Income from continuing operations per share:
Basic	$	0.30		$	0.12	$	0.86		$	0.48
Diluted	$	0.27		$	0.11	$	0.78		$	0.42
Loss from Discontinued Operations
Loss from discontinued operations	$	(728	)	$	—	$	(3,739	)	$	—
Less: loss allocated to participating securities	(96		)	—		(495		)	—
Loss from discontinued operations attributable to common stockholders	$	(632	)	$	—	$	(3,244	)	$	—
Loss from discontinued operations per share attributable to stockholders:
Basic	$	(0.05	)	$	—	$	(0.28	)	$	—
Diluted	$	(0.05	)	$	—	$	(0.25	)	$	—
Net income
Net income	$	3,288		$	1,634	$	7,850		$	6,570
Less: income allocated to participating securities	435			213		1,038			858
Net income attributable to common stockholders	$	2,853		$	1,421	$	6,812		$	5,712
Net income per share:
Basic	$	0.25		$	0.12	$	0.59		$	0.48
Diluted	$	0.22		$	0.11	$	0.53		$	0.42
Weighted Average Number of Common Shares Outstanding
Basic	11,600,189			11,828,657		11,643,664			11,814,045
Dilutive effect of stock options and warrants	1,210,190			1,424,080		1,185,230			1,673,604
Diluted	12,810,379			13,252,737		12,828,894			13,487,649

The following common share equivalents have been excluded from the calculation of weighted-average common shares outstanding, because the effect is anti-dilutive for the periods presented:



	Three Months Ended September 30,		Nine Months Ended September 30,
	2016	2017	2016	2017
Anti-dilutive Disclosure
Series A redeemable convertible preferred stock outstanding	1,775,000	1,775,000	1,775,000	1,775,000
Stock options issued and outstanding	569,947	110,125	569,947	110,125

Subsequent Events	9 Months Ended
Subsequent Events	Sep. 30, 2017
Subsequent Events [Abstract]
Subsequent Events	17. Subsequent Events On October 6, 2017, the Company was notified that certain additional jurisdictions within the state of Georgia intend to initiate legal proceedings against the Company in response to allegations that the Company failed to bill, collect and remit certain taxes and surcharges associated with the provision of 911 services. On October 13, 2017, the Company signed a tolling agreement with certain additional jurisdictions regarding such allegations. On October 19, 2017, the Company approved, and on October 23, 2017, the Company amended its Certificate of Incorporation allowing the Company to change the number of authorized shares as follows: (i) 30,000,000 shares of common stock, $0.001 par value per share of which 25,000,000 shares were designated as Old Class A common stock, and of which 5,000,000 shares were designated as Old Class B common stock and (ii) 1,200,000 shares of preferred stock, $0.001 par value. On October 19, 2017, the Company’s Board of Directors approved, and on October 23, 2017, the Company effected, a 2.50-to-1 split of its common stock. In connection with the common stock split, each share of outstanding common stock, option to purchase common stock and warrant to purchase common stock was increased to 2.50 shares of common stock and the exercise price of each outstanding option or warrant to purchase common stock was proportionately decreased. The stock split has been reflected retrospectively in these consolidated financial statements. In connection with the stock split, the conversion ratio of each share of outstanding Series A preferred stock was also adjusted such that each share of outstanding Series A preferred stock converts into 2.50 shares of Old Class A common stock after the 2.50-to-1 split. On October 27, 2017, the United States District Court for the Northern District of Texas granted Verizon’s motion to permit it to assert counterclaims against the Company in connection with the ongoing complaint related to unpaid intercarrier compensation charges. On November 9, 2017, the Company filed a second amended and restated certificate of incorporation. As a result of this amendment, the Company’s common stock consists of 120,000,000 authorized shares, par value $0.001 per share, of which the authorized New Class A common stock consists of 100,000,000 shares and the authorized New Class B common stock consists of 20,000,000 shares. On November 10, 2017, the Company sold 4,000,000 shares of its New Class A common stock at a public offering price of $20.00 per share. The Company received proceeds of $74,400, after deducting underwriting discounts and commissions of $5,600. Immediately prior to the pricing of the IPO on November 9, 2017, all shares of the Company’s then-outstanding Series A preferred stock converted into an aggregate of 1,775,000 shares of New Class B common stock and an aggregate of 11,811,480 shares of Old Class A common stock converted into New Class B common stock for a total of 13,586,480 shares outstanding of New Class B common stock. In addition, an aggregate of 34,840 shares of Old Class B common stock converted into New Class A common stock and warrants exercisable into shares of Old Class A common stock became exercisable into shares of New Class B common stock. On November 10, 2017 as a result of the Company's IPO the liability related to the Shareholders' anti-dilutive arrangement was terminated under the original terms of the agreement. On November 14, 2017, the Company paid in full its outstanding term loan of $38,500 with the proceeds from the IPO and wrote-off the unamortized loan fees associate with the term loan. The revolving loan remains in effect. On November 28, 2017, the Underwriters exercised their option to sell 162,991 shares of the Company's Class A common stock under the options granted to them under the Underwriting Agreement. As a result of this transaction, shares of New Class B common stock held by selling stockholders were converted into New Class A common stock. There were no additional proceeds to the Company as a result of the shares of New Class A common stock sold by the selling stockholders.

Summary of Significant Accounting Policies (Policies)	9 Months Ended
Summary of Significant Accounting Policies (Policies)	Sep. 30, 2017
Accounting Policies [Abstract]
Basis of Presentation	The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”) and applicable rules and regulations of the SEC regarding interim financial reporting. Certain information and note disclosures normally included in the financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. Therefore, these condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes included in the final prospectus filed with the SEC pursuant to Rule 424(b) under the Securities Act on November 13, 2017 (the “Prospectus”). The Company had no components of other comprehensive income during any of the periods presented, and as such, a separate consolidated statement of comprehensive income is not presented. The condensed consolidated balance sheet as of December 31, 2016, included herein, was derived from the audited financial statements as of that date, but does not include all disclosures including certain notes required by GAAP on an annual reporting basis. In the opinion of management, the accompanying unaudited condensed consolidated financial statements reflect all normal recurring adjustments necessary to present fairly the financial position, results of operations, comprehensive income and cash flows for the interim periods, but are not necessarily indicative of the results of operations to be anticipated for the full year 2017 or any future period.
Principles of Consolidation	The condensed consolidated financial statements include the accounts of Bandwidth Inc. and its wholly owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation.
Use of Estimates	The preparation of the Company’s consolidated financial statements in conformity with GAAP requires the Company to make estimates and judgments that affect the amounts reported in these financial statements and accompanying notes. Although the Company believes the estimates it uses are reasonable, due to the inherent uncertainty involved in making these estimates, actual results reported in future periods could differ from those estimates. These estimates in the condensed consolidated financial statements include, but are not limited to, allowance for doubtful accounts, recoverability of long-lived and intangible assets, customer relationship period, valuation allowances on tax assets, certain accrued expenses, and contingencies.
Concentration of Credit Risk	Financial instruments that are exposed to concentration of credit risk consist primarily of cash and cash equivalents and trade accounts receivable. Cash deposits may be in excess of insured limits. The Company believes that the financial institutions that hold its cash deposits are financially sound and, accordingly, minimal credit risk exists with respect to these balances. With regard to customers, credit evaluation and account monitoring procedures are used to minimize the risk of loss. The Company believes that no additional credit risk beyond amounts provided for by the allowance for doubtful accounts are inherent in accounts receivable.
Recent Accounting Pronouncements Not Yet Adopted	In May 2017, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2017-09, Compensation-Stock Compensation (Topic 718), Scope of Modification Accounting, which amends the scope of modification accounting for share-based payment arrangements. The ASU provides guidance on the types of changes to terms or conditions of share-based payment awards to which an entity would be required to apply modification accounting under ASC 718, Compensation-Stock Compensation. ASU 2017-09 is effective for fiscal years and interim periods within those years beginning after December 15, 2017, and early adoption is permitted. The Company is evaluating the impact of this guidance on its consolidated financial statements and related disclosures. In January 2017, the FASB issued ASU 2017-04, Simplifying the Test for Goodwill Impairment, which simplifies the accounting for goodwill impairment. The ASU requires impairment charges to be based on the first step in today’s two-step impairment test under Accounting Standards Codification (“ASC”) 350. ASU 2017-04 is effective for annual and interim impairment tests performed in periods beginning after December 15, 2021, and early adoption is permitted. The Company is evaluating the impact of this guidance on its consolidated financial statements and related disclosures. In January 2017, the FASB issued ASU 2017-01, Business Combinations (Topic 805) Clarifying the Definition of a Business, which amends the guidance of FASB Accounting Standards Codification Topic 805, “Business Combinations”, adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions or disposals of assets or businesses. The definition of a business affects many areas of accounting including acquisitions, disposals, goodwill, and consolidation. This guidance is effective for annual and interim periods beginning after December 15, 2017, and early adoption is permitted under certain circumstances. The adoption of this standard is dependent upon future transactions. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230), Classification of Certain Cash Receipts and Cash Payments, which clarifies how entities should classify certain cash receipts and cash payments on the statement of cash flows. The guidance also clarifies how the predominance principle should be applied when cash receipts and cash payments have aspects of more than one class of cash flows. ASU 2016-15 is effective for fiscal years beginning after December 15, 2018, and interim periods within fiscal years beginning after December 15, 2019, and early adoption is permitted. Entities will have to apply the guidance retrospectively, but if it is impracticable to do so for an issue, the amendments related to that issue would be applied prospectively. The Company is evaluating the impact of this guidance on its consolidated financial statements and related disclosures. In February 2016, the FASB issued ASU 2016-02, Leases. The standard will affect all entities that lease assets and will require lessees to recognize a lease liability and a right-of-use asset for all leases (except for short- term leases that have a duration of less than one year) as of the date on which the lessor makes the underlying asset available to the lessee. For lessors, accounting for leases is substantially the same as in prior periods. ASU 2016-02 is effective for fiscal years beginning after December 15, 2019, and interim periods within annual periods beginning after December 15, 2020, and early adoption is permitted. For leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements, lessees and lessors must apply a modified retrospective transition approach. While the Company expects the adoption of this standard to result in an increase to the reported assets and liabilities, it has not yet determined the full impact that the adoption of this standard will have on its financial statements and related disclosures. In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers. This new guidance will replace most existing. GAAP guidance on this topic. The new revenue recognition standard provides a unified model to determine when and how revenue is recognized. The core principle is that a company should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration for which the entity expects to be entitled in exchange for those goods or services. In August 2015, the FASB issued ASU 2015-14, Revenue from Contracts with Customers: Deferral of the effective date, which deferred by one year the effective date for the new revenue reporting standard for entities reporting under GAAP. In accordance with the deferral, this guidance will be effective beginning January 1, 2019. This guidance can be applied either retrospectively to each period presented or as a cumulative-effect adjustment as of the date of adoption. Early adoption is permitted beginning January 1, 2017. In December 2016, the FASB issued ASU 2016-20, Revenue from Contracts with Customers, Technical Corrections and Improvements to Topic 606, which made twelve additional technical corrections and improvements to the new revenue standard. In March 2016, the FASB issued ASU 2016-08, Revenue from Contracts with Customers, Principal versus Agent Considerations (Reporting Revenue Gross versus Net) clarifying the implementation guidance on principal versus agent considerations. Specifically, an entity is required to determine whether the nature of a promise is to provide the specified good or service itself (that is, the entity is a principal) or to arrange for the good or service to be provided to the customer by the other party (that is, the entity is an agent). The determination influences the timing and amount of revenue recognition. In April 2016, the FASB issued ASU 2016-10, Revenue from Contracts with Customers, Identifying Performance Obligations and Licensing, clarifying the implementation guidance on identifying performance obligations and licensing. Specifically, the amendments reduce the cost and complexity of identifying promised goods or services and improve the guidance for determining whether promises are separately identifiable. The amendments also provide implementation guidance on accounting for an entity’s promise to grant a license. In May 2016, the FASB issued ASU 2016-12, Revenue from Contracts with Customers, Narrow-Scope Improvements and Practical Expedients, clarifying guidance on assessing collectability, presentation of sales taxes, noncash consideration, completed contracts and contract modifications. The effective date and transition requirements for ASU 2016-20, ASU 2016-08 and ASU 2016-10 are the same as the effective date and transition requirements for ASU 2014-09. The Company is still assessing all potential impacts of the new standard on its consolidated financial statements. Given the comprehensive nature of the standard, the Company has already taken steps to begin assessing the impact on its consolidated financial results. It has completed a preliminary diagnostic, in order to highlight potential differences between current accounting policies and the new standard, and has begun drafting memos to document its accounting positions. Additionally, the Company engaged a third-party service provider to assist in its evaluation of customer contracts and to identify the attributes that could result in a different accounting treatment under ASU 2014-09. From an information technology perspective, the Company has identified a new technology solution which meets its business requirements and will be implemented to comply with ASC 2014-09. The Company has not reached a conclusion as to whether the quantitative effect of the adoption of the new standard on its revenue streams will be material. It will continue to monitor and assess the impact of the changes of the new standard and the related interpretations of its application as they become available.

Discontinued Operations (Tables)

9 Months Ended

Sep. 30, 2017

Discontinued Operations and Disposal Groups [Abstract]

Summary of Operating Results of the Discontinued Operations Through the Date of the Spin-Off

The table below provides the operating results of the discontinued operations for the three and nine months ended September 30, 2016:



	Three Months Ended September 30, 2016			Nine Months Ended September 30, 2016
Revenue	$	25,919		$	68,164
Direct costs of network services and equipment	(19,335		)	(50,823		)
Operating expense	(7,072		)	(20,312		)
Depreciation and interest	(240		)	(768		)
Loss from discontinued operations	$	(728	)	$	(3,739	)

- Definition

Tabular disclosure of information related to a disposal group. Includes, but is not limited to, a discontinued operation, disposal classified as held-for-sale or disposed of by means other than sale or disposal of an individually significant component.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=65878427&loc=SL51721533-107759

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
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-Section 50
-Paragraph 4B
-URI http://asc.fasb.org/extlink&oid=64827811&loc=SL51721665-107760

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=64827811&loc=d3e1474-107760

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=64827811&loc=d3e1361-107760

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=64827811&loc=SL51721683-107760

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 3A
-URI http://asc.fasb.org/extlink&oid=84176398&loc=SL51724579-110230

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 5C
-URI http://asc.fasb.org/extlink&oid=64827811&loc=SL51721675-107760

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 4A
-URI http://asc.fasb.org/extlink&oid=64827811&loc=SL51721663-107760

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=84176398&loc=d3e2941-110230

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 5B
-URI http://asc.fasb.org/extlink&oid=64827811&loc=SL51721673-107760

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 3A
-URI http://asc.fasb.org/extlink&oid=64827811&loc=SL51721659-107760

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 5A
-URI http://asc.fasb.org/extlink&oid=64827811&loc=SL51721671-107760

Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 5D
-URI http://asc.fasb.org/extlink&oid=64827811&loc=SL51721677-107760

+ Details

Fair Value of Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2017

Fair Value Disclosures [Abstract]

Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis

The following table summarizes the assets and liabilities measured at fair value as of December 31, 2016 and September 30, 2017:



	Fair Value Measurements on a Recurring Basis December 31, 2016
	Level 1		Level 2		Level 3			Total
Money Market Account	$	63	$	—	$	—		$	63
Shareholders’ anti-dilutive arrangement	—		—		(184		)	(184		)



	Fair Value Measurements on a Recurring Basis September 30, 2017
	Level 1		Level 2		Level 3			Total
Money Market Account	$	64	$	—	$	—		$	64
Shareholders’ anti-dilutive arrangement	—		—		(873		)	(873		)

Financial Statement Components (Tables)

9 Months Ended

Sep. 30, 2017

Financial Statement Components [Abstract]

Schedule of Allowance for Doubtful Accounts

Accounts receivable, net of allowance for doubtful accounts consisted of the following:



	December 31, 2016			September 30, 2017
Trade accounts receivable	$	31,734		$	40,351
Unbilled accounts receivable	7,368			7,859
Allowance for doubtful accounts	(22,571		)	(30,040		)
Other accounts receivable	307			532
Total accounts receivable, net	$	16,838		$	18,702

A roll forward of the components of the allowance for doubtful accounts for the three and nine months ended September 30, 2016 and 2017 are as follows:



	Three Months Ended September 30,						Nine Months Ended September 30,
Allowance for doubtful accounts:	2016			2017			2016			2017
Balance, beginning of period	$	182		$	112		$	238		$	255
Charged to bad debt expense	(87		)	83			45			95
Deductions(1)	(25		)	(19		)	(213		)	(174		)
Balance, end of period	$	70		$	176		$	70		$	176

________________________

(1) Write off of uncollectible accounts after all collection efforts have been exhausted.



	Three Months Ended September 30,						Nine Months Ended September 30,
Allowance for CABS revenue:	2016			2017			2016			2017
Balance, beginning of period	$	15,641		$	27,401		$	12,318		$	22,316
Billings deemed not probable of collection(1)	5,119			2,485			8,466			7,613
Deductions(2)	(1		)	(22		)	(25		)	(65		)
Balance, end of period	$	20,759		$	29,864		$	20,759		$	29,864

________________________

(1) Represents amounts billed but where collectibility is not probable based on customers collection experience. Amounts were charged to a contra-revenue account.

(2) Write off of uncollectible accounts after all collection efforts have been exhausted.



	Three Months Ended September 30,				Nine Months Ended September 30,
CABS revenue:	2016		2017		2016		2017
Billed	$	7,246	$	4,992	$	15,094	$	14,501
Revenue recognized	2,127		2,507		6,628		6,888
Billings deemed not probable of collection(1)	$	5,119	$	2,485	$	8,466	$	7,613

________________________

(1) Represents amounts billed but where collectibility is not probable based on customers collection experience. Amounts were charged to a contra-revenue account.

Schedule of Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following:



	December 31, 2016		September 30, 2017
Accrued expense	$	6,853	$	8,319
Accrued compensation and benefits(1)	4,373		4,656
Accrued sales, use, and telecom related taxes	2,769		2,325
Other accrued expenses	654		483
Total accrued expenses	$	14,649	$	15,783

________________________

(1) On September 1, 2017, the Company reached a separation agreement with one of its executives. The agreement resulted in a severance liability of approximately $660 as of September 30, 2017.

Property and Equipment (Tables)

9 Months Ended

Sep. 30, 2017

Property, Plant and Equipment [Abstract]

Summary of Property and Equipment, Net

Property and equipment, net consisted of the following:



	December 31, 2016			September 30, 2017
Furniture and fixtures	$	680		$	680
Computer and office equipment	7,539			7,525
Telecommunications equipment	13,718			16,815
Leasehold improvements	453			453
Software development costs	13,677			15,198
Automobile	10			10
Total cost	36,077			40,681
Less—accumulated depreciation	(24,896		)	(28,292		)
Total property and equipment, net	$	11,181		$	12,389

The Company recognized depreciation expense, which includes amortization of capitalized software development costs, as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
	2016		2017		2016		2017
Cost of revenue	$	1,155	$	1,161	$	3,514	$	3,245
Research and development	15		29		64		51
Sales and marketing	6		6		15		20
General and administrative	149		45		506		327
Total depreciation expense	$	1,325	$	1,241	$	4,099	$	3,643

Summary of Depreciation Expense

Property and equipment, net consisted of the following:



	December 31, 2016			September 30, 2017
Furniture and fixtures	$	680		$	680
Computer and office equipment	7,539			7,525
Telecommunications equipment	13,718			16,815
Leasehold improvements	453			453
Software development costs	13,677			15,198
Automobile	10			10
Total cost	36,077			40,681
Less—accumulated depreciation	(24,896		)	(28,292		)
Total property and equipment, net	$	11,181		$	12,389

The Company recognized depreciation expense, which includes amortization of capitalized software development costs, as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
	2016		2017		2016		2017
Cost of revenue	$	1,155	$	1,161	$	3,514	$	3,245
Research and development	15		29		64		51
Sales and marketing	6		6		15		20
General and administrative	149		45		506		327
Total depreciation expense	$	1,325	$	1,241	$	4,099	$	3,643

Intangible Assets (Tables)

9 Months Ended

Sep. 30, 2017

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Indefinite-Lived Intangible Assets

Intangible assets consisted of the following as of December 31, 2016:



	Gross Amount		Accumulated Amortization			Net Carrying Value		Amortization Period
								(Years)
Customer relationships	$	10,396	$	(3,032	)	$	7,364	20
Domain name and related trademarks	2,678		(2,324		)	354		3–7
Licenses, amortizable	341		(341		)	—		2
Non-compete agreements	139		(139		)	—		2–5
Developed technology	775		(775		)	—		3
Licenses, indefinite lived	764		—			764		Indefinite
Total intangible assets, net	$	15,093	$	(6,611	)	$	8,482

Intangible assets consisted of the following as of September 30, 2017:



	Gross Amount		Accumulated Amortization			Net Carrying Value		Amortization Period
								(Years)
Customer relationships	$	10,396	$	(3,422	)	$	6,974	20
Domain name and related trademarks	2,678		(2,563		)	115		3–7
Licenses, amortizable	341		(341		)	—		2
Non-compete agreements	139		(139		)	—		2–5
Developed technology	775		(775		)	—		3
Licenses, indefinite lived	764		—			764		Indefinite
Total intangible assets, net	$	15,093	$	(7,240	)	$	7,853

Schedule of Finite-Lived Intangible Assets

Intangible assets consisted of the following as of December 31, 2016:



	Gross Amount		Accumulated Amortization			Net Carrying Value		Amortization Period
								(Years)
Customer relationships	$	10,396	$	(3,032	)	$	7,364	20
Domain name and related trademarks	2,678		(2,324		)	354		3–7
Licenses, amortizable	341		(341		)	—		2
Non-compete agreements	139		(139		)	—		2–5
Developed technology	775		(775		)	—		3
Licenses, indefinite lived	764		—			764		Indefinite
Total intangible assets, net	$	15,093	$	(6,611	)	$	8,482

Intangible assets consisted of the following as of September 30, 2017:



	Gross Amount		Accumulated Amortization			Net Carrying Value		Amortization Period
								(Years)
Customer relationships	$	10,396	$	(3,422	)	$	6,974	20
Domain name and related trademarks	2,678		(2,563		)	115		3–7
Licenses, amortizable	341		(341		)	—		2
Non-compete agreements	139		(139		)	—		2–5
Developed technology	775		(775		)	—		3
Licenses, indefinite lived	764		—			764		Indefinite
Total intangible assets, net	$	15,093	$	(7,240	)	$	7,853

Schedule of Future Estimated Amortization Expense

Future estimated amortization expense subsequent to September 30, 2017 is as follows:



	Amount
2017 (remaining three months)	$	209
2018	555
2019	520
2020	520
2021	520
Thereafter	4,765
	$	7,089

Debt (Tables)

9 Months Ended

Sep. 30, 2017

Debt Disclosure [Abstract]

Schedule of Future Payments Under the Term Loan

Future payments under the term loan subsequent to September 30, 2017 are as follows:



	Amount
2017 (remaining three months)	$	500
2018	3,000
2019	3,000
2020	4,000
2021	28,000
	$	38,500

Schedule of Remaining Payments due on Capital Lease Obligations

Remaining payments due on the Company’s capital lease obligations as of September 30, 2017, are as follows:



	Amount
2017	$	25
2018	91
Less amount representing interest	—
	116
Less current maturities	99
	$	17

Segment and Geographic Information (Tables)

9 Months Ended

Sep. 30, 2017

Segment Reporting [Abstract]

Schedule of Segment Reporting Information, by Segment



	Three Months Ended September 30,				Nine Months Ended September 30,
	2016		2017		2016		2017
CPaaS
Revenue	$	30,249	$	33,397	$	86,900	$	96,591
Cost of revenue	18,197		19,247		53,576		56,394
Gross profit	$	12,052	$	14,150	$	33,324	$	40,197
Other
Revenue	$	8,354	$	7,941	$	26,473	$	23,898
Cost of revenue	3,317		3,324		10,601		10,037
Gross profit	$	5,037	$	4,617	$	15,872	$	13,861
Consolidated
Revenue	$	38,603	$	41,338	$	113,373	$	120,489
Cost of revenue	21,514		22,571		64,177		66,431
Gross profit	$	17,089	$	18,767	$	49,196	$	54,058

Schedule of Revenue by Geographical Area

The Company generates its revenue primarily in the United States. Revenue by geographical area is detailed in the table below (which is determined based on the customer billing address):



	Three Months Ended September 30,				Nine Months Ended September 30,
	2016		2017		2016		2017
United States	$	38,408	$	41,188	$	113,027	$	120,090
International	195		150		346		399
Total	$	38,603	$	41,338	$	113,373	$	120,489

Stock Based Compensation (Tables)

9 Months Ended

Sep. 30, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of Fair Value of Options Granted Using the Black-Scholes-Merton Pricing Model for Valuation Assumptions

The fair value of options granted is estimated on the date of grant using the Black-Scholes-Merton option pricing model based on the assumptions in the table below:



	Three Months Ended September 30,		Nine Months Ended September 30,
	2016	2017	2016	2017
Expected dividend yield	0%	0%	0%	0%
Expected stock price volatility	44%	47%-49%	44%	44%-49%
Average risk-free interest rate	1.3%	1.9%	1.3%–1.6%	1.9%–2.3%
Expected life	6.2 years	6.2 years	6.2 years	6.2 years
Fair value of common stock	$9.57	$18.40-$20.83	$9.57	$9.60-$20.83

Summary of Stock Option Activity

The following summarizes the stock option activity for the periods presented:



	Number of Options Outstanding		Weighted- Average Exercise Price (per share)		Weighted- Average Remaining Contract Life (in years)	Aggregate Intrinsic value (in thousands)
Balance, December 31, 2016	3,582,241		$	6.54	5.12	$	11,049
Grants	179,922		13.79
Exercised	(58,162	)	5.27			445
Forfeited or cancelled	(41,115	)	9.48
Balance, September 30, 2017	3,662,886		$	6.88	4.63	$	51,292
Options vested and exercisable at September 30, 2017	3,159,450		$	6.23	4.01	$	46,326
Options vested and expected to vest as of September 30, 2017	3,640,526		$	6.85	4.60	$	51,092

Schedule of Stock-Based Compensation Expense in Continuing Operations

The Company recognized total stock-based compensation expense in continuing operations as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
	2016		2017		2016		2017
Cost of revenue	$	17	$	17	$	45	$	57
Research and development	30		38		108		100
Sales and marketing	37		54		142		124
General and administrative(1)	161		503		804		821
Total	$	245	$	612	$	1,099	$	1,102

________________________

Commitments and Contingencies (Tables)

9 Months Ended

Sep. 30, 2017

Commitments and Contingencies Disclosure [Abstract]

Schedule of Future Minimum Lease Payments for Operating Leases

Future minimum lease payments required under operating leases as of September 30, 2017, for each of the years ending December 31, are as follows:



	Amount
2017	$	905
2018	3,631
2019	3,700
2020	3,838
2021	3,873
2022 and thereafter	2,018
	$	17,965

Schedule of Future Minimum Lease Receipts for Operating Lease

Future minimum sub-lease receipts as of September 30, 2017 for each of the years ending December 31, are as follows:



	Amount
2017	$	251
2018	1,020
2019	1,042
2020	1,065
2021	1,089
2022 and thereafter	594
	$	5,061

Basic and Diluted Income (Loss) per Common Share (Tables)

9 Months Ended

Sep. 30, 2017

Earnings Per Share [Abstract]

Schedule of Earnings Per Share, Basic and Diluted

The components of basic and diluted earnings per share, or EPS, are as follows:



	Three Months Ended September 30,					Nine Months Ended September 30,
	2016			2017		2016			2017
Income from Continuing Operations
Income from continuing operations	$	4,016		$	1,634	$	11,589		$	6,570
Less: income allocated to participating securities	531			213		1,533			858
Income from continuing operations attributable to common stockholders	$	3,485		$	1,421	$	10,056		$	5,712
Income from continuing operations per share:
Basic	$	0.30		$	0.12	$	0.86		$	0.48
Diluted	$	0.27		$	0.11	$	0.78		$	0.42
Loss from Discontinued Operations
Loss from discontinued operations	$	(728	)	$	—	$	(3,739	)	$	—
Less: loss allocated to participating securities	(96		)	—		(495		)	—
Loss from discontinued operations attributable to common stockholders	$	(632	)	$	—	$	(3,244	)	$	—
Loss from discontinued operations per share attributable to stockholders:
Basic	$	(0.05	)	$	—	$	(0.28	)	$	—
Diluted	$	(0.05	)	$	—	$	(0.25	)	$	—
Net income
Net income	$	3,288		$	1,634	$	7,850		$	6,570
Less: income allocated to participating securities	435			213		1,038			858
Net income attributable to common stockholders	$	2,853		$	1,421	$	6,812		$	5,712
Net income per share:
Basic	$	0.25		$	0.12	$	0.59		$	0.48
Diluted	$	0.22		$	0.11	$	0.53		$	0.42
Weighted Average Number of Common Shares Outstanding
Basic	11,600,189			11,828,657		11,643,664			11,814,045
Dilutive effect of stock options and warrants	1,210,190			1,424,080		1,185,230			1,673,604
Diluted	12,810,379			13,252,737		12,828,894			13,487,649

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share

The following common share equivalents have been excluded from the calculation of weighted-average common shares outstanding, because the effect is anti-dilutive for the periods presented:



	Three Months Ended September 30,		Nine Months Ended September 30,
	2016	2017	2016	2017
Anti-dilutive Disclosure
Series A redeemable convertible preferred stock outstanding	1,775,000	1,775,000	1,775,000	1,775,000
Stock options issued and outstanding	569,947	110,125	569,947	110,125

Organization and Description of Business (Details) $ / shares in Units, $ in Thousands			9 Months Ended
	Nov. 10, 2017 USD ($) $ / shares shares	Nov. 09, 2017 USD ($) vote_per_share vote $ / shares shares	Sep. 30, 2017 segment
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of operating segments \| segment			2
Number of reportable segments \| segment			2
Subsequent Event \| IPO
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds from initial public offering \| $	$ 74,400	$ 74,400
Subsequent Event \| IPO \| Common Class B
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Reclassification of shares ratio		1
Votes per share of stock held \| vote_per_share		10
Common stock, shares outstanding (in shares)		1
Subsequent Event \| IPO \| Common Class A
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Reclassification of shares ratio		1
Votes per share of stock held \| vote_per_share		1
Common stock, shares outstanding (in shares)		1
Subsequent Event \| IPO \| New Common Class A
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Reclassification of shares ratio		1
Votes per share of stock held \| vote		1
Shares issued (in shares)	4,000,000	4,000,000
Shares issued, price (in usd per share) \| $ / shares	$ 20.00	$ 20

Discontinued Operations (Details) $ in Thousands		3 Months Ended		9 Months Ended
Discontinued Operations (Details) $ in Thousands	Nov. 30, 2016	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss from discontinued operations		$ 0	$ (728)	$ 0	$ (3,739)
Discontinued Operations, Disposed of by Means Other than Sale, Spinoff
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenue			25,919		68,164
Direct costs of network services and equipment			(19,335)		(50,823)
Operating expense			(7,072)		(20,312)
Depreciation and interest			$ (240)		$ (768)
Republic
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Common stock, conversion basis ratio	1

- Definition

Amount after tax of income (loss) from a discontinued operation attributable to the parent. Includes, but is not limited to, the income (loss) from operations during the phase-out period, gain (loss) on disposal, gain (loss) for reversal of write-down (write-down) to fair value, less cost to sell, and adjustments to a prior period gain (loss) on disposal.

+ References + Details

Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Shareholder agreement, term of notice (in days)		90 days
Shareholder agreement, qualified public offering threshold		$ 20,000
Other Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Change in fair value of the Level 3 liability	$ 136	689
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money Market Account	64	64	$ 63
Shareholders’ anti-dilutive arrangement	(873)	(873)	(184)
Fair Value, Measurements, Recurring \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money Market Account	64	64	63
Shareholders’ anti-dilutive arrangement	0	0	0
Fair Value, Measurements, Recurring \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money Market Account	0	0	0
Shareholders’ anti-dilutive arrangement	0	0	0
Fair Value, Measurements, Recurring \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money Market Account	0	0	0
Shareholders’ anti-dilutive arrangement	$ (873)	$ (873)	$ (184)

Financial Statement Components - Accounts Receivable, Net of Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financial Statement Components [Abstract]
Trade accounts receivable	$ 40,351	$ 31,734
Unbilled accounts receivable	7,859	7,368
Allowance for doubtful accounts	(30,040)	(22,571)
Other accounts receivable	532	307
Total accounts receivable, net	$ 18,702	$ 16,838

Financial Statement Components - Allowance For Doubtful Accounts (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Allowance for Doubtful Accounts Receivable [Roll Forward]
Revenue	$ 41,338	$ 38,603	$ 120,489	$ 113,373
Carrier Access Billing (CAB)
Allowance for Doubtful Accounts Receivable [Roll Forward]
Billings deemed not probable of collection(1)	2,485	5,119	7,613	8,466
Billed	4,992	7,246	14,501	15,094
Revenue	2,507	2,127	6,888	6,628
Accounts Receivable, Excluding Carrier Access Billing (CAB)
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period	112	182	255	238
Billings deemed not probable of collection(1)	83	(87)	95	45
Deductions	(19)	(25)	(174)	(213)
Balance, end of period	176	70	176	70
Carrier Access Billing (CAB)
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period	27,401	15,641	22,316	12,318
Billings deemed not probable of collection(1)	2,485	5,119	7,613	8,466
Deductions	(22)	(1)	(65)	(25)
Balance, end of period	$ 29,864	$ 20,759	$ 29,864	$ 20,759

Financial Statement Components - Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financial Statement Components [Abstract]
Accrued expense	$ 8,319	$ 6,853
Accrued compensation and benefits	4,656	4,373
Accrued sales, use, and telecom related taxes	2,325	2,769
Other accrued expenses	483	654
Total accrued expenses	15,783	$ 14,649
Severance liability	$ 660

Property and Equipment - Summary of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 40,681	$ 36,077
Less—accumulated depreciation	(28,292)	(24,896)
Total property and equipment, net	12,389	11,181
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	680	680
Computer and office equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	7,525	7,539
Telecommunications equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	16,815	13,718
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	453	453
Software development costs
Property, Plant and Equipment [Line Items]
Property and equipment, gross	15,198	13,677
Automobile
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 10	$ 10

Property and Equipment - Software Development Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Property, Plant and Equipment [Abstract]
Capitalized amount of software development costs	$ 988	$ 612	$ 2,586	$ 1,537
Amortization of capitalized software development costs	$ 524	$ 929	$ 1,659	$ 2,766

Property and Equipment - Depreciation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Depreciation Expense [Line Items]
Depreciation	$ 1,241	$ 1,325	$ 3,643	$ 4,099
Cost of revenue
Depreciation Expense [Line Items]
Depreciation	1,161	1,155	3,245	3,514
Research and development
Depreciation Expense [Line Items]
Depreciation	29	15	51	64
Sales and marketing
Depreciation Expense [Line Items]
Depreciation	6	6	20	15
General and administrative
Depreciation Expense [Line Items]
Depreciation	$ 45	$ 149	$ 327	$ 506

Intangible Assets - Summary of Intangible Assets (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Accumulated Amortization	$ (7,240)	$ (6,611)
Finite-lived intangible assets, net	7,089
Gross Amount	15,093	15,093
Net Carrying Value	7,853	8,482
Licenses
Indefinite-lived Intangible Assets [Line Items]
Licenses, indefinite lived	764	764
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	10,396	10,396
Accumulated Amortization	(3,422)	(3,032)
Finite-lived intangible assets, net	$ 6,974	$ 7,364
Amortization Period	20 years	20 years
Domain name and related trademarks
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	$ 2,678	$ 2,678
Accumulated Amortization	(2,563)	(2,324)
Finite-lived intangible assets, net	$ 115	$ 354
Domain name and related trademarks \| Minimum
Finite-Lived Intangible Assets [Line Items]
Amortization Period	3 years	3 years
Domain name and related trademarks \| Maximum
Finite-Lived Intangible Assets [Line Items]
Amortization Period	7 years	7 years
Licenses
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	$ 341	$ 341
Accumulated Amortization	(341)	(341)
Finite-lived intangible assets, net	$ 0	$ 0
Amortization Period	2 years	2 years
Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	$ 139	$ 139
Accumulated Amortization	(139)	(139)
Finite-lived intangible assets, net	$ 0	$ 0
Non-compete agreements \| Minimum
Finite-Lived Intangible Assets [Line Items]
Amortization Period	2 years	2 years
Non-compete agreements \| Maximum
Finite-Lived Intangible Assets [Line Items]
Amortization Period	5 years	5 years
Developed technology
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	$ 775	$ 775
Accumulated Amortization	(775)	(775)
Finite-lived intangible assets, net	$ 0	$ 0
Amortization Period	3 years	3 years

Intangible Assets - Amortization Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense	$ 210	$ 222	$ 629	$ 669
Weighted average amortization period			19 years

Intangible Assets - Future Estimated Amortization Expense (Details) $ in Thousands	Sep. 30, 2017 USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2017 (remaining three months)	$ 209
2018	555
2019	520
2020	520
2021	520
Thereafter	4,765
Finite-lived intangible assets, net	$ 7,089

Debt - Narrative (Details) - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Revolving Credit Facility
Debt Instrument [Line Items]
Long-term line of credit	$ 0	$ 5,000,000
Available borrowing capacity	25,000,000
Unamortized loan fees, line of credit arrangements	163,000	199,000
Secured Debt
Debt Instrument [Line Items]
Long-term debt	38,500,000	40,000,000
Unamortized loan fees	$ 266,000	$ 326,000

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References + Details

Debt - Future Payments Under the Term Loan (Details) - Secured Debt - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
2017 (remaining three months)	$ 500
2018	3,000
2019	3,000
2020	4,000
2021	28,000
Total	$ 38,500	$ 40,000

Debt - Capital Leases (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Debt Disclosure [Abstract]
Cost of assets under capital leases	$ 1,951	$ 1,951
Accumulated depreciation of assets under capital leases	$ 1,865	$ 1,807

Debt - Remaining Payments due on Capital Lease Obligations (Details)	Sep. 30, 2017 USD ($)
Debt Disclosure [Abstract]
2017	$ 25,000
2018	91,000
Less amount representing interest	0
Capital lease obligations	116,000
Less current maturities	99,000
Capital lease obligations, noncurrent	$ 17,000

Segment and Geographic Information - Reconciliation of Segment Profit (Loss) (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) segment	Sep. 30, 2016 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments \| segment			2
Revenue	$ 41,338	$ 38,603	$ 120,489	$ 113,373
Cost of revenue	22,571	21,514	66,431	64,177
Gross profit	18,767	17,089	54,058	49,196
CPaaS
Segment Reporting Information [Line Items]
Revenue	33,397	30,249	96,591	86,900
Cost of revenue	19,247	18,197	56,394	53,576
Gross profit	14,150	12,052	40,197	33,324
Other
Segment Reporting Information [Line Items]
Revenue	7,941	8,354	23,898	26,473
Cost of revenue	3,324	3,317	10,037	10,601
Gross profit	$ 4,617	$ 5,037	$ 13,861	$ 15,872

Segment and Geographic Information - Reconciliation of Revenue by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 41,338	$ 38,603	$ 120,489	$ 113,373
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	41,188	38,408	120,090	113,027
International
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 150	$ 195	$ 399	$ 346

Redeemable Convertible Preferred Stock and Stockholder's Deficit (Details)	Nov. 10, 2017 shares	Nov. 09, 2017 vote $ / shares shares	Oct. 23, 2017 $ / shares shares	Sep. 30, 2017 $ / shares shares	Dec. 31, 2016 $ / shares shares
Class of Stock [Line Items]
Common stock reserved for the issuance of stock purchase warrants (in shares)					64,691
Stock Purchase Warrant
Class of Stock [Line Items]
Common stock reserved for the issuance of stock purchase warrants (in shares)				64,691	64,691
Series A Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares outstanding (in shares)				710,000	710,000
Preferred stock, shares issued (in shares)				710,000	710,000
Convertible preferred stock, conversion price (in usd per share) \| $ / shares				$ 30.8358	$ 30.8358
Old Common Class A
Class of Stock [Line Items]
Common stock, shares issued (in shares)				11,811,480	11,779,975
Common stock, shares outstanding (in shares)				11,811,480	11,779,975
Common stock, par value (in usd per share) \| $ / shares				$ 0.001	$ 0.001
Old Common Class B
Class of Stock [Line Items]
Common stock, shares issued (in shares)				34,840	18,590
Common stock, shares outstanding (in shares)				34,840	18,590
Common stock, par value (in usd per share) \| $ / shares				$ 0.001	$ 0.001
Subsequent Event
Class of Stock [Line Items]
Stock split conversion ratio			2.5
Common stock, par value (in usd per share) \| $ / shares		$ 0.001	$ 0.001
Common stock, shares authorized (in shares)		120,000,000	30,000,000
Shares converted (in shares)		1,775,000
Subsequent Event \| Series A Preferred Stock
Class of Stock [Line Items]
Convertible preferred stock, conversion price (in usd per share) \| $ / shares			$ 12.3343
Shares converted (in shares)	1,775,000
Subsequent Event \| Old Common Class A
Class of Stock [Line Items]
Common stock, shares authorized (in shares)			25,000,000
Shares converted (in shares)	11,811,480
Subsequent Event \| Old Common Class A \| IPO
Class of Stock [Line Items]
Reclassification of shares ratio		1
Subsequent Event \| Old Common Class B
Class of Stock [Line Items]
Common stock, shares authorized (in shares)			5,000,000
Subsequent Event \| Old Common Class B \| IPO
Class of Stock [Line Items]
Reclassification of shares ratio		1
Shares converted (in shares)	34,840
Subsequent Event \| New Common Class B
Class of Stock [Line Items]
Common stock, shares authorized (in shares)		20,000,000
Shares converted (in shares)	13,586,480
Subsequent Event \| New Common Class B \| IPO
Class of Stock [Line Items]
Reclassification of shares ratio		1
Votes per share of stock held \| vote		10
Subsequent Event \| New Common Class A
Class of Stock [Line Items]
Common stock, shares authorized (in shares)		100,000,000
Shares converted (in shares)	34,840
Subsequent Event \| New Common Class A \| IPO
Class of Stock [Line Items]
Reclassification of shares ratio		1
Votes per share of stock held \| vote		1

Stock Based Compensation (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		9 Months Ended
	Aug. 24, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Estimated grant date fair value of options vested		$ 443	$ 188	$ 1,070	$ 1,900
2010 Equity Compensation Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant-date fair value of stock options granted (in usd per share)		$ 9.45	$ 4.03	$ 7.48	$ 4.04
2010 Equity Compensation Plan \| Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance (in shares)	3,466,275
Vesting period (in years)	4 years
Contractual life (in years)	10 years

Stock Based Compensation - Fair Value of Options Granted Using the Black-Scholes Pricing Model (Details) - Employee Stock Option - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield	0.00%	0.00%	0.00%	0.00%
Expected stock price volatility		44.00%		44.00%
Average risk-free interest rate	1.90%	1.30%
Average risk-free interest rate, minimum			1.90%	1.30%
Average risk-free interest rate, maximum			2.30%	1.60%
Expected life (in years)	6 years 2 months 12 days	6 years 2 months 12 days	6 years 2 months 12 days	6 years 2 months 12 days
Fair value of common stock (in usd per share)		$ 9.57		$ 9.57
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected stock price volatility	47.00%		44.00%
Fair value of common stock (in usd per share)	$ 18.40		$ 9.60
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected stock price volatility	49.00%		49.00%
Fair value of common stock (in usd per share)	$ 20.83		$ 20.83

Stock Based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Number of options outstanding, beginning balance (in shares)		3,582,241
Number of options, granted (in shares)	179,922
Number of options exercised (in shares)	(58,162)
Number of options, forfeited or cancelled (in shares)	(41,115)
Number of options outstanding, ending balance (in shares)	3,662,886
Number of options outstanding, options vested and exercisable (in shares)	3,159,450
Number of options outstanding, options vested and expected to vest (in shares)	3,640,526
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted-average exercise price, ending balance (in usd per share)		$ 6.54
Weighted-average exercise price, granted (in usd per share)	$ 13.79
Weighted-average exercise price, exercised (in usd per share)	5.27
Weighted-average exercise price, forfeited or cancelled (in usd per share)	9.48
Weighted-average exercise price, ending balance (in usd per share)	6.88
Weighted-average exercise price, options vested and exercisable (in usd per share)	6.23
Weighted-average exercise price, options vested and expected to vest (in usd per share)	$ 6.85
Weighted-average remaining contract life, options outstanding (in years)	4 years 7 months 17 days	5 years 1 month 13 days
Weighted-average remaining contract life, options vested and exercisable (in years)	4 years 4 days
Weighted-average remaining contract life, options vested and expected to vest (in years)	4 years 7 months 6 days
Aggregate intrinsic value, options outstanding	$ 51,292		$ 11,049
Aggregate intrinsic value, options exercised	445
Aggregate intrinsic value, options vested and exercisable	46,326
Aggregate intrinsic value, options vested and expected to vest	$ 51,092

Stock Based Compensation - Allocated Stock Based Compensation Expense (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	Sep. 01, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Allocated share-based compensation expense	$ 394	$ 612	$ 245	$ 1,102	$ 1,099
Number of options outstanding (in shares)	194,234	3,662,886		3,662,886		3,582,241
Unrecognized cost for stock based compensation		$ 2,191		$ 2,191
Cost of revenue
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Allocated share-based compensation expense		17	17	57	45
Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Allocated share-based compensation expense		38	30	100	108
Selling and marketing
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Allocated share-based compensation expense		54	37	124	142
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Allocated share-based compensation expense		$ 503	$ 161	$ 821	$ 804
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Unrecognized cost for stock based compensation, period for recognition (in years)				2 years 8 months 12 days

Commitments and Contingencies - Operating Leases (Details)		3 Months Ended		9 Months Ended
	Apr. 14, 2017 ft²	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)
Lessee, Lease, Description [Line Items]
Rent expense		$ 1,034,000	$ 666,000	$ 2,414,000	$ 1,512,000
Reduction of rent expense					$ 0
General and administrative
Lessee, Lease, Description [Line Items]
Reduction of rent expense		$ 251,000		$ 697,000
Amended Operating Lease Agreement, Original
Lessee, Lease, Description [Line Items]
Term of lease (in months)	63 months
Office space (in square foot) \| ft²	40,657
Amended Operating Lease Agreement, Extension
Lessee, Lease, Description [Line Items]
Office space (in square foot) \| ft²	128,200

Commitments and Contingencies - Future Minimum Rental Payments for Operating Leases (Details) $ in Thousands	Sep. 30, 2017 USD ($)
Commitments and Contingencies Disclosure [Abstract]
2017	$ 905
2018	3,631
2019	3,700
2020	3,838
2021	3,873
2022 and thereafter	2,018
Future minimum payments due, total	$ 17,965

Commitments and Contingencies - Future Minimum Lease Receipts (Details) $ in Thousands	Sep. 30, 2017 USD ($)
Commitments and Contingencies Disclosure [Abstract]
2017	$ 251
2018	1,020
2019	1,042
2020	1,065
2021	1,089
2022 and thereafter	594
Future minimum lease receipts, total	$ 5,061

Commitments and Contingencies - Contractual Obligations (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2017 USD ($)
Other Commitments [Line Items]
Annual minimum commitments	$ 1,200
Term of agreement (in years)	5 years
Capital Addition Purchase Commitments
Other Commitments [Line Items]
Non-cancellable purchase obligation	$ 5,308

Employee Benefit Plan (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
Employee Benefit Plan (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Retirement Benefits [Abstract]
Matching contributions	$ 181	$ 161	$ 596	$ 543

Income Taxes (Details)	3 Months Ended		9 Months Ended
Income Taxes (Details)	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Tax Disclosure [Abstract]
Effective income tax rate	35.50%	3.30%	37.20%	3.40%
Federal statutory rate	34.00%	34.00%	34.00%	34.00%

Related Parties (Details) - USD ($)	3 Months Ended	9 Months Ended
Related Parties (Details) - USD ($)	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Related Party Transaction [Line Items]
Rental payments received			$ 0
General and administrative
Related Party Transaction [Line Items]
Rental payments received	$ 251,000	$ 697,000
Affiliated Entity \| Republic \| Transition Services Agreement
Related Party Transaction [Line Items]
Revenue from related parties	37,000	548,000
Due from related parties	35,000	35,000
Affiliated Entity \| Republic \| Facilities Sharing Agreement
Related Party Transaction [Line Items]
Rental payments received	251,000	697,000
Due from related parties	0	0		$ 0
Affiliated Entity \| Republic \| Tax Sharing Agreement
Related Party Transaction [Line Items]
Due from related parties	0	0		0
Due to related parties	0	0		$ 0
Affiliated Entity \| Republic \| Master Services Agreement
Related Party Transaction [Line Items]
Revenue from related parties	550,000	1,623,000
Due from related parties	$ 193,000	$ 193,000

Basic and Diluted Income (Loss) per Common Share - Components of Basic and Diluted Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income from Continuing Operations
Income from continuing operations	$ 1,634	$ 4,016	$ 6,570	$ 11,589
Less: income allocated to participating securities	213	531	858	1,533
Income from continuing operations attributable to common stockholders	$ 1,421	$ 3,485	$ 5,712	$ 10,056
Income from continuing operations per share:
Basic (in usd per share)	$ 0.12	$ 0.30	$ 0.48	$ 0.86
Diluted (in usd per share)	$ 0.11	$ 0.27	$ 0.42	$ 0.78
Loss from Discontinued Operations
Loss from discontinued operations	$ 0	$ (728)	$ 0	$ (3,739)
Less: loss allocated to participating securities	0	(96)	0	(495)
Loss from discontinued operations attributable to common stockholders	$ 0	$ (632)	$ 0	$ (3,244)
Loss from discontinued operations per share attributable to stockholders:
Basic (in usd per share)	$ 0.00	$ (0.05)	$ 0	$ (0.28)
Diluted (in usd per share)	$ 0.00	$ (0.05)	$ 0	$ (0.25)
Net income
Net income	$ 1,634	$ 3,288	$ 6,570	$ 7,850
Less: income allocated to participating securities	213	435	858	1,038
Net income attributable to common stockholders	$ 1,421	$ 2,853	$ 5,712	$ 6,812
Net income per share:
Basic (in usd per share)	$ 0.12	$ 0.25	$ 0.48	$ 0.59
Diluted (in usd per share)	$ 0.11	$ 0.22	$ 0.42	$ 0.53
Weighted Average Number of Common Shares Outstanding
Basic (in shares)	11,828,657	11,600,189	11,814,045	11,643,664
Dilutive effect of stock options and warrants (in shares)	1,424,080	1,210,190	1,673,604	1,185,230
Diluted (in shares)	13,252,737	12,810,379	13,487,649	12,828,894

Basic and Diluted Income (Loss) per Common Share - Antidilutive Securities Excluded from the Computation (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Series A redeemable convertible preferred stock outstanding
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from calculation of weighted-average common shares outstanding	1,775,000	1,775,000	1,775,000	1,775,000
Stock options issued and outstanding
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from calculation of weighted-average common shares outstanding	110,125	569,947	110,125	569,947

Subsequent Events (Details) $ / shares in Units, $ in Thousands	Nov. 28, 2017 shares	Nov. 14, 2017 USD ($)	Nov. 10, 2017 USD ($) $ / shares shares	Nov. 09, 2017 USD ($) $ / shares shares	Oct. 23, 2017 $ / shares shares	Sep. 30, 2017 $ / shares	Dec. 31, 2016 $ / shares
Old Common Class A
Subsequent Event [Line Items]
Common stock, par value (in usd per share) \| $ / shares						$ 0.001	$ 0.001
Old Common Class B
Subsequent Event [Line Items]
Common stock, par value (in usd per share) \| $ / shares						$ 0.001	$ 0.001
Subsequent Event
Subsequent Event [Line Items]
Common stock, shares authorized (in shares)				120,000,000	30,000,000
Common stock, par value (in usd per share) \| $ / shares				$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)					1,200,000
Preferred stock, par value (in usd per share) \| $ / shares					$ 0.001
Stock split conversion ratio					2.5
Shares converted (in shares)				1,775,000
Subsequent Event \| Secured Debt
Subsequent Event [Line Items]
Long-term debt \| $		$ 38,500
Subsequent Event \| Old Common Class A
Subsequent Event [Line Items]
Common stock, shares authorized (in shares)					25,000,000
Shares converted (in shares)			11,811,480
Subsequent Event \| Old Common Class B
Subsequent Event [Line Items]
Common stock, shares authorized (in shares)					5,000,000
Subsequent Event \| New Common Class A
Subsequent Event [Line Items]
Common stock, shares authorized (in shares)				100,000,000
Shares converted (in shares)			34,840
Subsequent Event \| New Common Class B
Subsequent Event [Line Items]
Common stock, shares authorized (in shares)				20,000,000
Shares converted (in shares)			13,586,480
Subsequent Event \| Series A Preferred Stock
Subsequent Event [Line Items]
Shares converted (in shares)			1,775,000
Subsequent Event \| IPO
Subsequent Event [Line Items]
Proceeds from initial public offering \| $			$ 74,400	$ 74,400
Underwriting discounts and commissions \| $			$ 5,600
Subsequent Event \| IPO \| Old Common Class B
Subsequent Event [Line Items]
Shares converted (in shares)			34,840
Subsequent Event \| IPO \| New Common Class A
Subsequent Event [Line Items]
Shares issued, price (in usd per share) \| $ / shares			$ 20.00	$ 20
Sale of stock, number of shares issued (in shares)			4,000,000	4,000,000
Subsequent Event \| Over-Allotment Option \| Common Class A
Subsequent Event [Line Items]
Sale of stock, number of shares issued (in shares)	162,991