Consolidated Statements of Convertible Preferred Stock and Stockholders’ Equity (Deficit) - USD ($) shares in Thousands	Preferred Stock Convertible preferred stock	Preferred Stock C and D	Preferred Stock E	Preferred Stock F	Common stock	Additional Paid-in Capital	Notes Receivable from Officers	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Convertible preferred stock	E	F	Total
Balance at Dec. 31, 2012	$ 10,516,000				$ 1,000	$ 1,422,000	$ (192,000)		$ (137,546,000)				$ (136,315,000)
Balance (in shares) at Dec. 31, 2012					5,849
Convertible Preferred Stock Balance (in shares) at Dec. 31, 2012	11,572
Issuance of convertible preferred stock		$ 139,664,000	$ 35,019,000
Issuance of convertible preferred stock (in shares)		9,592	5,884
Issuance of common stock upon exercise of stock options	$ 0				$ 0	259,000	0	$ 0	0				259,000
Issuance of common stock upon exercise of stock options (in shares)	0				712
Stock based compensation						1,657,000							1,657,000
Issuance costs of Series F Preferred Stock											$ (405,371)
Net loss									(37,110,000)				(37,110,000)
Balance at Dec. 31, 2013	$ 185,199,000				$ 1,000	3,338,000	(192,000)		(174,656,000)				(171,509,000)
Balance (in shares) at Dec. 31, 2013					6,561
Convertible preferred stock balance (in shares) at Dec. 31, 2013	27,048
Issuance of convertible preferred stock				$ 55,413,000
Issuance of convertible preferred stock (in shares)				4,349
Issuance of common stock upon exercise of stock options	$ 0				$ 0	169,000	0	0	0				169,000
Issuance of common stock upon exercise of stock options (in shares)	0				318
Stock based compensation						5,157,000							5,157,000
Issuance costs of Series F Preferred Stock												$ (86,933)
Net loss									(5,152,000)				(5,152,000)
Balance at Dec. 31, 2014	$ 240,612,000				$ 1,000	8,664,000	(192,000)		(179,808,000)				$ (171,335,000)
Balance (in shares) at Dec. 31, 2014					6,879								6,879
Convertible preferred stock balance at Dec. 31, 2014										$ 240,612,000	$ 35,019,000	$ 55,413,000	$ 240,612,000
Convertible preferred stock balance (in shares) at Dec. 31, 2014	31,397												31,397
Issuance of common stock upon exercise of stock options						1,258,000							$ 1,258,000
Issuance of common stock upon exercise of stock options (in shares)					1,170
Stock based compensation						7,326,000							7,326,000
Issuance costs of Series F Preferred Stock				$ (27,000)
Officer loan receivable repayment							$ 192,000						192,000
Issuance of common stock in connection with the initial public offering					$ 1,000	182,465,000							182,466,000
Issuance of common stock in connection with the initial public offering (in shares)					10,900
Issuance costs of Initial Public Offering						(4,036,000)							(4,036,000)
Conversion of all Preferred Stock into Common Stock upon the completion of the initial public offering	$ (240,585,000)				$ 3,000	240,582,000							240,585,000
Conversion of all Preferred Stock into Common Stock upon the completion of the initial public offering (in shares)	(31,397)				31,397
Net loss									(70,275,000)				(70,275,000)
Accumulated other comprehensive income (loss)								(1,416,000)					(1,416,000)
Balance at Dec. 31, 2015					$ 5,000	$ 436,259,000		$ (1,416,000)	$ (250,083,000)				$ 184,765,000
Balance (in shares) at Dec. 31, 2015					50,346								50,346