Fair Value of Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2017

Fair Value Disclosures [Abstract]

Liabilities Measured at Fair Value on a Recurring Basis

The following table sets forth the measurement at fair value on a recurring basis of the investments in money market fund and U.S. government securities. The securities are categorized as a Level 1 asset, as their valuation is based on quoted prices for identical assets in active markets. See "Note 4 — Cash and Cash Equivalents".

Assets Measured at Fair Value on a Recurring Basis as of December 31, 2017

	Quoted Prices in Active  Markets for Identical Assets (Level 1)		Significant Other Observable  Inputs (Level 2)		Significant Unobservable  Inputs (Level 3)		Balance as of December 31, 2017
	(in thousands)
Assets
Cash and cash equivalents	$	183,369	$	—	$	—	$	183,369
Total	$	183,369	$	—	$	—	$	183,369

The following table sets forth the measurement at fair value on a recurring basis of the contingent cash consideration due the selling unitholders of Cogent related to the Earnout. The liability arose as a result of the Acquisition and is categorized as a Level 3 liability. See "Note 3 — Acquisition".

Liabilities Measured at Fair Value on a Recurring Basis as of December 31, 2017

	Quoted Prices in Active  Markets for Identical Assets (Level 1)		Significant Other Observable  Inputs (Level 2)		Significant Unobservable  Inputs (Level 3)		Balance as of December 31, 2017
	(in thousands)
Liabilities
Contingent obligation due selling unitholders of Cogent	$	—	$	—	$	13,763	$	13,763
Total	$	—	$	—	$	13,763	$	13,763

Liabilities Measured at Fair Value on a Recurring Basis as of December 31, 2016

	Quoted Prices in Active  Markets for Identical Assets (Level 1)		Significant Other Observable  Inputs (Level 2)		Significant Unobservable  Inputs (Level 3)		Balance as of December 31, 2016
	(in thousands)
Liabilities
Contingent obligation due selling unitholders of Cogent	$	—	$	—	$	15,095	$	15,095
Total	$	—	$	—	$	15,095	$	15,095

Changes in Level 3 Measured at Fair Value

Changes in Level 3 liabilities measured at fair value on a recurring basis for the year ended December 31, 2017 are as follows:

	Opening Balance as of January 1, 2017		Total realized and unrealized gains (losses) included in Net Income		Unrealized gains (losses) included in Other Comprehensive Income		Purchases		Issues		Sales		Settlements		Closing Balance as of December 31, 2017		Unrealized gains (losses) for Level 3 liabilities outstanding at December 31, 2017
	(in thousands)
Liabilities
Contingent obligation due selling unitholders of Cogent	$	15,095	$	1,332	$	—	$	—	$	—	$	—	$	—	$	13,763	$	1,332
Total	$	15,095	$	1,332	$	—	$	—	$	—	$	—	$	—	$	13,763	$	1,332

Changes in Level 3 liabilities measured at fair value on a recurring basis for the year ended December 31, 2016 are as follows:

	Opening Balance as of January 1, 2016		Total realized and unrealized gains (losses) included in Net Income			Unrealized gains (losses) included in Other Comprehensive Income		Purchases		Issues		Sales		Settlements		Closing Balance as of December 31, 2016		Unrealized gains (losses) for Level 3 liabilities outstanding at December 31, 2016
	(in thousands)
Liabilities
Contingent obligation due selling unitholders of Cogent	$	13,647	$	(1,448	)	$	—	$	—	$	—	$	—	$	—	$	15,095	$	(1,448	)
Total	$	13,647	$	(1,448	)	$	—	$	—	$	—	$	—	$	—	$	15,095	$	(1,448	)

Quantitative Information

The following tables presents quantitative information about the significant unobservable inputs utilized by the Company in the fair value measure of Level 3 liabilities measured at fair value on a recurring basis, as of December 31, 2017:

	Fair Value as of December 31, 2017		Valuation Technique(s)	Unobservable  Input(s)		Range (Weighted Average)
	(in thousands)
Liabilities
Contingent obligation due selling unitholders of Cogent	$	13,763	Present value of expected payments	Discount rate		13	%
				Forecast revenue	(a)

The following tables presents quantitative information about the significant unobservable inputs utilized by the Company in the fair value measure of Level 3 liabilities measured at fair value on a recurring basis, as of December 31, 2016:

	Fair Value as of December 31, 2016		Valuation Technique(s)	Unobservable  Input(s)		Range (Weighted Average)
	(in thousands)
Liabilities
Contingent obligation due selling unitholders of Cogent	$	15,095	Present value of expected payments	Discount rate		13	%
				Forecast revenue	(a)

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(a) The Company's estimate of contingent consideration as of December 31, 2017 and December 31, 2016 was principally based on the acquired business' (i) actual revenue generation from April 1, 2015 through March 31, 2017 and (ii) actual and projected revenue generation from April 1, 2017 through March 31, 2019.