Consolidated Statements of Changes in Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Redeemable Convertible Preferred Stock [Member]	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income [Member]	Accumulated Deficit [Member]
Temporary equity, Beginning Balance at Dec. 31, 2014		$ 211,598
Temporary equity, Beginning Balance, shares at Dec. 31, 2014		16,382,000
Beginning Balance at Dec. 31, 2014	$ (246,862)		$ 126	$ (3,526)	$ 0	$ 0	$ (243,462)
Beginning Balance, shares at Dec. 31, 2014			12,563,000	402,000
Stock-based compensation	10,685				10,685
Accretion of preferred stock to redemption value		$ 35,061
Accretion of preferred stock to redemption value	(35,061)				(2,203)		(32,858)
Conversion of preferred stock to common stock, shares		(16,382,000)
Conversion of preferred stock to common stock, shares			16,382,000
Conversion of preferred stock to common stock		$ (246,659)
Conversion of preferred stock to common stock	246,659		$ 164		246,495
IPO participation payment and beneficial conversion charge	0		$ 19		14,142		(14,161)
IPO participation payment and beneficial conversion charge, shares			1,940,000
Issuance of common stock in relation to IPO and concurrent private placement, net of offering costs	112,275		$ 77		112,198
Issuance of common stock in relation to IPO and concurrent private placement, net of offering costs , shares			7,730,000
Issuance of common stock and options associated with acquisitions	31,975		$ 13		31,962
Issuance of common stock and options associated with acquisitions, shares			1,262,000
Issuance of restricted stock	0		$ 13		(13)
Issuance of restricted stock, shares			1,358,000
Shares withheld for employee taxes	(3,087)		$ (1)		(3,086)
Shares withheld for employee taxes, shares			(134,000)
Issuance of common stock upon exercise of stock options and warrants	1,348		$ 4		1,344
Issuance of common stock upon exercise of stock options and warrants, shares			439,000
Net loss	(49,857)						(49,857)
Temporary equity, Ending Balance at Dec. 31, 2015		$ 0
Temporary equity, Ending Balance, shares at Dec. 31, 2015		0
Ending Balance at Dec. 31, 2015	68,075		$ 415	$ (3,526)	411,524	0	(340,338)
Ending Balance, shares at Dec. 31, 2015			41,540,000	402,000
Stock-based compensation	17,316				17,316
Issuance of common stock under ESPP	3,724		$ 4		3,720
Issuance of common stock under ESPP, shares			346,000
Vesting of restricted stock units	0		$ 1		(1)
Vesting of restricted stock units, shares			91,000
Forfeiture of restricted stock awards	0
Forfeiture of restricted stock awards, shares			(27,000)
Shares withheld for employee taxes	(1,026)		$ (1)	$ (865)	(160)
Shares withheld for employee taxes, shares			(74,000)	(62,000)
Excess tax benefit from stock-based compensation	87				87
Issuance of common stock upon exercise of stock options and warrants	2,881		$ 7		2,874
Issuance of common stock upon exercise of stock options and warrants, shares			679,000
Net unrealized loss on investments	(19)					(19)
Net loss	$ (49,000)						(49,000)
Temporary equity, Ending Balance at Dec. 31, 2016		$ 0
Temporary equity, Ending Balance, shares at Dec. 31, 2016	0	0
Ending Balance at Dec. 31, 2016	$ 42,038		$ 426	$ (4,391)	435,360	(19)	(389,338)
Ending Balance, shares at Dec. 31, 2016			42,555,000	464,000
Stock-based compensation	19,541				19,541
Issuance of common stock under ESPP	2,914		$ 3		2,911
Issuance of common stock under ESPP, shares			247,000
Vesting of restricted stock units	0		$ 4		(4)
Vesting of restricted stock units, shares			436,000
Forfeiture of restricted stock awards	0
Forfeiture of restricted stock awards, shares			(21,000)
Shares withheld for employee taxes	(698)		$ (1)	$ (373)	(324)
Shares withheld for employee taxes, shares			(50,000)	(23,000)
Issuance of common stock upon exercise of stock options and warrants	5,848		$ 9		5,839
Issuance of common stock upon exercise of stock options and warrants, shares			887,000
Net unrealized loss on investments	(20)					(20)
Net loss	$ (45,470)						(45,470)
Temporary equity, Ending Balance at Dec. 31, 2017		$ 0
Temporary equity, Ending Balance, shares at Dec. 31, 2017	0	0
Ending Balance at Dec. 31, 2017	$ 24,153		$ 441	$ (4,764)	463,428	(39)	$ (434,913)
Ending Balance, shares at Dec. 31, 2017			44,054,000	487,000
Cumulative-effect adjustment for the adoption of ASU 2016-09	$ 0				$ 105	$ (105)