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, 2014	$ 97,243		$ 2	$ 256,388	$ (157,658)	$ (1,489)
Beginning balance, shares at Dec. 31, 2014			26,895,480
Proceeds from follow-on public offering, net of offering costs	127,854		$ 1	127,853
Proceeds from follow-on public offering, net of offering costs, shares			3,450,000
Issuance of common stock under employee equity plans, net of repurchases	12,652			12,652
Issuance of common stock under employee equity plans, net of repurchases, shares			1,074,862
Vesting of restricted stock	767			767
Stock-based compensation	38,801			38,801
Income tax (deficiencies) benefit from employee stock option exercises	60			60
Shares withheld for tax withholding on vesting of restricted stock units	(7,221)			(7,221)
Components of other comprehensive income (loss), net of tax
Change in unrealized gain (loss) on investments	(54)					(54)
Change in unrealized loss on hedging instruments	425					425
Net loss	(43,101)				(43,101)
Comprehensive loss	(42,730)
Ending balance at Sep. 30, 2015	227,426		$ 3	429,300	(200,759)	(1,118)
Ending balance, shares at Sep. 30, 2015			31,420,342
Beginning balance at Jun. 30, 2015						(974)
Components of other comprehensive income (loss), net of tax
Change in unrealized gain (loss) on investments	8
Change in unrealized loss on hedging instruments	(152)
Net loss	(5,747)
Comprehensive loss	(5,891)
Ending balance at Sep. 30, 2015	227,426		$ 3	429,300	(200,759)	(1,118)
Ending balance, shares at Sep. 30, 2015			31,420,342
Beginning balance at Dec. 31, 2015	240,201	[1]	$ 3	448,069	(206,540)	(1,331)
Beginning balance, shares at Dec. 31, 2015			31,837,144
Issuance of common stock under employee equity plans, net of repurchases	8,106			8,106
Issuance of common stock under employee equity plans, net of repurchases, shares			790,023
Issuance of holdback shares in connection with acquisitions, shares			206,499
Stock-based compensation	42,612			42,612
Income tax (deficiencies) benefit from employee stock option exercises	(29)			(29)
Shares withheld for tax withholding on vesting of restricted stock units	(6,520)			(6,520)
Components of other comprehensive income (loss), net of tax
Change in unrealized gain (loss) on investments	76					76
Change in unrealized loss on hedging instruments	486					486
Net loss	(60,461)				(60,461)
Comprehensive loss	(59,899)
Ending balance at Sep. 30, 2016	224,471		$ 3	492,238	(267,001)	(769)
Ending balance, shares at Sep. 30, 2016			32,833,666
Beginning balance at Jun. 30, 2016						(863)
Components of other comprehensive income (loss), net of tax
Change in unrealized gain (loss) on investments	(130)
Change in unrealized loss on hedging instruments	224
Net loss	(11,738)
Comprehensive loss	(11,644)
Ending balance at Sep. 30, 2016	$ 224,471		$ 3	$ 492,238	$ (267,001)	$ (769)
Ending balance, shares at Sep. 30, 2016			32,833,666

[1] The Condensed Consolidated Balance Sheet as of December 31, 2015 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements.