Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning balance at Dec. 31, 2016	$ 231,963	$ 3	$ 510,257	$ (276,819)	$ (1,478)
Beginning balance, shares at Dec. 31, 2016		33,088,990
Cumulative effect of a change in accounting principle	14		2,601	(2,587)
Issuance of common stock under employee equity plans, net of repurchases	14,851		14,851
Issuance of common stock under employee equity plans, net of repurchases, shares		724,907
Stock-based compensation	25,117		25,117
Shares withheld for tax withholding on vesting of restricted stock units	(6,621)		(6,621)
Component of other comprehensive income (loss), net of tax
Change in unrealized gain (loss) on investments	50				50
Change in unrealized gain (loss) on hedging instruments	2,148				2,148
Net (loss) income	19,593			19,593
Comprehensive (loss) income	21,791
Ending balance at Jun. 30, 2017	287,115	$ 3	546,205	(259,813)	720
Ending balance, shares at Jun. 30, 2017		33,813,897
Beginning balance at Mar. 31, 2017					279
Component of other comprehensive income (loss), net of tax
Change in unrealized gain (loss) on investments	22
Change in unrealized gain (loss) on hedging instruments	419
Net (loss) income	(3,490)
Comprehensive (loss) income	(3,049)
Ending balance at Jun. 30, 2017	287,115	$ 3	546,205	(259,813)	720
Ending balance, shares at Jun. 30, 2017		33,813,897
Beginning balance at Dec. 31, 2017	315,117	$ 3	572,106	(256,537)	(455)
Beginning balance, shares at Dec. 31, 2017		34,233,888
Cumulative effect of a change in accounting principle	19,473			19,473
Issuance of common stock under employee equity plans, net of repurchases	9,995		9,995
Issuance of common stock under employee equity plans, net of repurchases, shares		722,587
Stock-based compensation	25,950		25,950
Shares withheld for tax withholding on vesting of restricted stock units	(6,753)		(6,753)
Component of other comprehensive income (loss), net of tax
Change in unrealized gain (loss) on investments	(229)				(229)
Change in unrealized gain (loss) on hedging instruments	(2,278)				(2,278)
Net (loss) income	(32,840)			(32,840)
Comprehensive (loss) income	(35,347)
Ending balance at Jun. 30, 2018	328,435	$ 3	601,298	(269,904)	(2,962)
Ending balance, shares at Jun. 30, 2018		34,956,475
Beginning balance at Mar. 31, 2018					(1,262)
Component of other comprehensive income (loss), net of tax
Change in unrealized gain (loss) on investments	167
Change in unrealized gain (loss) on hedging instruments	(1,867)
Net (loss) income	(23,059)
Comprehensive (loss) income	(24,759)
Ending balance at Jun. 30, 2018	$ 328,435	$ 3	$ 601,298	$ (269,904)	$ (2,962)
Ending balance, shares at Jun. 30, 2018		34,956,475