Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Stockholder Note Receivable [Member]	Non-Controlling Interest [Member]	Other Comprehensive Loss [Member]	Accumulated Deficit [Member]	Redeemable Convertible Preferred Stock [Member]
Redeemable Convertible Preferred Stock, Ending balance at Dec. 31, 2012								$ 63,225
Redeemable Convertible Preferred Stock, Ending balance, shares at Dec. 31, 2012								55,211,585
Beginning balance at Dec. 31, 2012	$ (64,554)	$ 1	$ 5	$ (69)	$ 25		$ (64,516)
Beginning balance, Shares at Dec. 31, 2012		788,946
Issuance of Series D and E redeemable convertible preferred stock for cash	2,431				2,431			$ 36,683
Issuance of Series D and E redeemable convertible preferred stock for cash, Shares								14,504,841
Issuance of Series D redeemable convertible preferred stock for conversion of debt and interest								$ 9,537
Issuance of Series D redeemable convertible preferred stock for conversion of debt and interest, Shares								3,770,989
Series D and E redeemable convertible preferred stock issuance costs	(65)				(65)			$ (389)
Exercise of common stock options	77		54		23
Exercise of common stock options, Shares		67,645
Changes in share repurchase liability	(3)		(3)
Stock-based compensation	155		155
Accretion to redemption value of redeemable convertible preferred stock	(1,637)		(366)				(1,271)	1,637
Capital contribution related to reversal of historical accretion of redeemable convertible preferred stock	17,528		17,528					(17,528)
Net loss	(20,014)						(20,014)
Redeemable Convertible Preferred Stock, Ending balance at Dec. 31, 2013								$ 93,165
Redeemable Convertible Preferred Stock, Ending balance, shares at Dec. 31, 2013								73,487,415
Ending balance at Dec. 31, 2013	(66,082)	$ 1	17,373	(69)	2,414		(85,801)
Ending balance, Shares at Dec. 31, 2013		856,591
Exercise of common stock options	72		43		29
Exercise of common stock options, Shares		53,289
Changes in share repurchase liability	13		13
Stock-based compensation	1,791		1,791
Dissolution of Affiliates	(2,038)		405		$ (2,443)			$ 2,038
Accretion to redemption value of redeemable convertible preferred stock	(416)		(416)					416
Net loss	(24,350)						(24,350)
Redeemable Convertible Preferred Stock, Ending balance at Dec. 31, 2014	95,619							$ 95,619
Redeemable Convertible Preferred Stock, Ending balance, shares at Dec. 31, 2014								73,487,415
Ending balance at Dec. 31, 2014	(91,010)	$ 1	19,209	(69)			(110,151)
Ending balance, Shares at Dec. 31, 2014		909,880
Issuance of Series D and E redeemable convertible preferred stock for cash								$ 75,650
Issuance of Series D and E redeemable convertible preferred stock for cash, Shares								68,166,894
Conversion of redeemable convertible preferred stock in connection with IPO	171,284	$ 16	171,268					$ (171,284)
Conversion of redeemable convertible preferred stock in connection with IPO, Shares		16,279,859						(141,654,309)
Issuance of common stock through initial public offering, net	75,903	$ 6	75,897
Issuance of common stock through initial public offering, net, Shares		6,164,000
Repayment of stockholder note receivable	60		(9)	$ 69
Exercise of common stock options	$ 535	$ 1	534
Exercise of common stock options, Shares	197,253	196,500
Reclassification of preferred stock warrant liability to additional paid-in-capital	$ 290		290
Issuance of common stock to The Scripps Research Institute	1,411		1,411
Issuance of common stock to The Scripps Research Institute, Share		119,840
Changes in share repurchase liability	(120)		(120)
Stock-based compensation	4,856		4,856
Accretion to redemption value of redeemable convertible preferred stock	(15)		(15)					$ 15
Change in unrealized loss on available for sale investments	(171)					$ (171)
Net loss	(47,973)						(47,973)
Redeemable Convertible Preferred Stock, Ending balance, shares at Dec. 31, 2015								0
Ending balance at Dec. 31, 2015	$ 115,050	$ 24	$ 273,321			$ (171)	$ (158,124)
Ending balance, Shares at Dec. 31, 2015		23,670,079