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	7,149		7,149
Issuance of common stock under employee equity plans, net of repurchases, shares		365,552
Stock-based compensation	13,610		13,610
Shares withheld for tax withholding on vesting of restricted stock units	(4,632)		(4,632)
Component of other comprehensive income (loss), net of tax
Change in unrealized gain (loss) on investments	28				28
Change in unrealized gain (loss) on hedging instruments	1,729				1,729
Net (loss) income	23,083			23,083
Comprehensive (loss) income	24,840
Ending balance at Mar. 31, 2017	272,944	$ 3	528,985	(256,323)	279
Ending balance, shares at Mar. 31, 2017		33,454,542
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	5,293		5,293
Issuance of common stock under employee equity plans, net of repurchases, shares		500,067
Stock-based compensation	14,637		14,637
Shares withheld for tax withholding on vesting of restricted stock units	(5,671)		(5,671)
Component of other comprehensive income (loss), net of tax
Change in unrealized gain (loss) on investments	(396)				(396)
Change in unrealized gain (loss) on hedging instruments	(411)				(411)
Net (loss) income	(9,781)			(9,781)
Comprehensive (loss) income	(10,588)
Ending balance at Mar. 31, 2018	$ 338,261	$ 3	$ 586,365	$ (246,845)	$ (1,262)
Ending balance, shares at Mar. 31, 2018		34,733,955