Statements of convertible preferred stock and preferred units, and stockholders' and members' equity (deficit) - USD ($) $ in Thousands	Total	Class A Units [Member]	Common Stock [Member]	Additional paid in capital [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Deficit [Member]	Series A Preferred Stock [Member]	Series B Preferred Stock [Member]	Series A Convertible Preferred Stock [Member]	Series B Convertible Preferred Stock [Member]	Series C Convertible Preferred Stock [Member]	Series D Convertible Preferred Stock [Member]	Convertible Preferred Stock And Preferred Units [Member]
Balances (Shares) at December 31, 2012 at Dec. 31, 2012							119,656,000
Balances at December 31, 2012 at Dec. 31, 2012							$ 3,499						$ 3,499
Issuance of convertible preferred stock, shares		19,476,000						24,155,000
Issuance of convertible preferred stock, net of transaction costs		$ 288				$ (288)		$ 1,965					1,965
Issuance of convertible preferred stock for the conversion of outstanding related party debt, Shares								71,160,000
Issuance of convertible preferred stock for the conversion of outstanding related party debt								$ 5,892					5,892
Accretion of preferred units	$ (422)					(422)	$ 280	$ 142					422
Net loss	(5,387)					(5,387)
Balances (Shares) at December 31, 2013 at Dec. 31, 2013							119,656,000	95,315,000
Balances at December 31, 2013 at Dec. 31, 2013							$ 3,779	$ 7,999					11,778
Balances (Shares) at December 31, 2012 at Dec. 31, 2012		112,672,000
Balances at December 31, 2012 at Dec. 31, 2012	(8,112)	$ 10,597				(18,709)
Balances (Shares) at December 31, 2013 at Dec. 31, 2013		132,148,000
Balances at December 31, 2013 at Dec. 31, 2013	(13,921)	$ 10,885				(24,806)
Accretion of preferred units	(815)			$ (815)					$ 184	$ 631			815
Net loss	$ (4,003)					(4,003)
Balances (Shares) at December 31, 2013 at Dec. 31, 2014	0								2,393,000	1,906,000
Balances at December 31, 2013 at Dec. 31, 2014	$ 12,593								$ 3,963	$ 8,630			12,593
Conversion from LLC to C corporation, Shares		(132,148,000)	2,643,000				(119,656,000)	(95,315,000)	2,393,000	1,906,000
Conversion from LLC to C corporation		$ (10,885)		10,885			$ (3,779)	$ (7,999)	$ 3,779	$ 7,999
Exercise of stock options	1			1
Stock-based compensation expense	319			319
Balances (Shares) at December 31, 2013 at Dec. 31, 2014			2,645,000
Balances at December 31, 2013 at Dec. 31, 2014	(18,291)			10,518		(28,809)
Discount on Related Party Promissory Notes	128			128
Exercise of stock options, Shares			2,000
Issuance of convertible preferred stock, shares			7,245,000								4,047,000	7,367,000
Issuance of convertible preferred stock, net of transaction costs	145,184		$ 1	145,183							$ 26,021		26,021
Issuance of convertible preferred stock, net of transaction costs												$ 67,998	67,998
Issuance of convertible preferred stock for the conversion of outstanding related party debt, Shares											585,000
Issuance of convertible preferred stock for the conversion of outstanding related party debt											$ 3,792		3,792
Accretion of preferred units	(1,747)			(1,747)					(2,280)	1,338	$ 187	$ 2,502	1,747
Net loss	$ (22,811)					(22,811)
Balances (Shares) at December 31, 2013 at Dec. 31, 2015	0
Exercise of stock options	$ 107			107
Stock-based compensation expense	2,921			2,921
Loss (gain) on extinguishment of convertible preferred stock	759			759					$ 1,317	$ (2,076)			(759)
Conversion of convertible preferred stock into common stock upon initial public offering, Shares			16,298,000						(2,393,000)	(1,906,000)	(4,632,000)	(7,367,000)
Conversion of convertible preferred stock into common stock upon initial public offering	111,392		$ 2	111,390					$ (3,000)	$ (7,892)	$ (30,000)	$ (70,500)	$ (111,392)
Unrealized loss on available-for-sale securities	(719)				$ (719)
Balances (Shares) at December 31, 2013 at Dec. 31, 2015			26,313,000
Balances at December 31, 2013 at Dec. 31, 2015	216,808		$ 3	269,144	$ (719)	$ (51,620)
Discount on Related Party Promissory Notes	$ 13			$ 13
Exercise of stock options, Shares			125,000