CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY - USD ($) $ in Thousands	Preferred Stock Series F Preferred Stock	Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Total
BALANCE at Dec. 31, 2012		$ 102,552	$ 1	$ 8,915	$ (96,337)	$ (87,421)
BALANCE, Shares at Dec. 31, 2012		43,636,635	8,939,067
Issuance of common stock for stock option exercises, net of repurchases				679		$ 679
Issuance of common stock for stock option exercises, net of repurchases, Shares			569,096			695,482
Vesting of early exercised stock options and restricted stock			$ 1	946		$ 947
Vesting of early exercised stock options and restricted stock, Shares			1,500,120
Issuance of Series F preferred stock at $9.9550 per share—net of issuance costs	$ 57,707
Issuance of Series E or F preferred stock at $9.9550 per share - net of issuance costs (in Shares)	5,809,437
Stock-based compensation				8,467		8,467
Net loss					(32,497)	(32,497)
BALANCE at Dec. 31, 2013		$ 160,259	$ 2	19,007	(128,834)	(109,825)
BALANCE, Shares at Dec. 31, 2013		49,446,072	11,008,283
Issuance of common stock for stock option exercises, net of repurchases				2,280		$ 2,280
Issuance of common stock for stock option exercises, net of repurchases, Shares			1,044,087			1,089,708
Vesting of early exercised stock options and restricted stock				669		$ 669
Vesting of early exercised stock options and restricted stock, Shares			1,400,259
Issuance of Series F preferred stock at $9.9550 per share—net of issuance costs	$ 1,994
Issuance of Series E or F preferred stock at $9.9550 per share - net of issuance costs (in Shares)	200,903
Stock-based compensation				16,749		16,749
Conversion of preferred stock for initial public offering		$ (162,253)	$ 5	162,248		162,253
Conversion of preferred stock for initial public offering, Shares		(49,646,975)	49,646,975
Issuance of common stock for initial public offering, net of issuance costs of $4,076			$ 1	102,874		102,875
Issuance of common stock for initial public offering, net of issuance costs of $4,076, Shares			12,777,777
Purchase of Averail Corporation				1,982		1,982
Purchase of Averail Corporation			276,463
Net loss					(61,889)	(61,889)
BALANCE at Dec. 31, 2014			$ 8	305,809	(190,723)	115,094
BALANCE, Shares at Dec. 31, 2014			76,153,844
Issuance of common stock for stock option exercises, net of repurchases				5,846		$ 5,846
Issuance of common stock for stock option exercises, net of repurchases, Shares			2,776,221			2,817,915
Vesting of early exercised stock options and restricted stock				246
Vesting of early exercised stock options and restricted stock, Shares			198,564
Issuance of common stock pursuant to the Employee Stock Purchase Plan				7,359		$ 7,359
Issuance of common stock pursuant to the Employee Stock Purchase Plan, Shares			1,273,147
Vesting of restricted stock units						246
Vesting of restricted stock units, Shares			924,461
Stock-based compensation				24,076		24,076
Net loss					(84,482)	(84,482)
BALANCE at Dec. 31, 2015			$ 8	$ 343,336	$ (275,205)	$ 68,139
BALANCE, Shares at Dec. 31, 2015			81,326,237