Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Novartis [Member] Collaborative Arrangement [Member]	Caribou agreements [Member]	Junior Preferred Units [Member] Caribou agreements [Member]	Common Units [Member]	Common Stock [Member]	Incentive [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]	Series A-1, Series A-2 and Junior Preferred [Member]	Series A-1, Series A-2 and Junior Preferred [Member] Novartis [Member] Collaborative Arrangement [Member]	Class A-1 and Class A-2 Preferred Units [Member]	Class A-2 Preferred Units [Member]	Series B Preferred Stock [Member]	Convertible Preferred Stock (Series B, Series A-2, Series A-1, Junior and Founder) [Member]
Beginning balance at May. 06, 2014	$ 0
Issuance of Junior Preferred Units in connection with the Caribou agreements			$ 4,055	$ 4,055
Issuance of Junior Preferred Units in connection with the Caribou agreements, units				8,110,599
Issuance of Preferred Units	12,393											$ 12,393
Issuance of Preferred Units, shares												11,238,095
Issuance of units/stock	349				$ 349
Issuance of units/stock, shares					946,237
Equity-based compensation	308				$ 258		$ 50
Equity-based compensation, shares					1,351,763		1,558,498
Net loss	(9,539)								$ (9,539)
Ending balance at Dec. 31, 2014	7,566				$ 607		$ 50		(9,539)	$ 16,448
Ending balance, shares at Dec. 31, 2014					2,298,000		1,558,498			19,348,694
Issuance of units/stock	1,984												$ 1,984
Issuance of units/stock, shares													1,333,333
Allocation from Novartis collaboration to carrying value of Preferred Shares	2,600	$ 2,644									$ 2,644
Tax provision associated with intraperiod tax allocation	(1,012)									$ (1,012)
Effect of Reorganization	(20,671)				$ (607)		$ (50)	$ 50		$ (20,064)					$ 20,671
Effect of Reorganization, shares					(2,298,000)	1,713,104	(1,558,498)			(20,682,027)					22,980,027
Issuance of Series B Preferred Shares, net of issuance costs														$ 67,263
Issuance of Series B Preferred Shares, net of issuance costs, shares														13,336,601
Equity-based compensation	685							685							$ 623
Equity-based compensation, shares						845,651
Net loss	(12,397)								(12,397)
Ending balance at Dec. 31, 2015	88,557														$ 88,557
Ending balance at Dec. 31, 2015	$ (21,201)							735	(21,936)
Ending balance, shares at Dec. 31, 2015															36,316,628
Ending balance, shares at Dec. 31, 2015	2,558,755					2,558,755
Conversion of convertible preferred stock	$ 88,557					$ 3		88,554							$ (88,557)
Conversion of convertible preferred stock, shares						23,481,956									(36,316,628)
Issuance of units/stock	167,139					$ 1		167,138
Issuance of units/stock, shares						9,955,554
Exercise of stock options	$ 2							2
Exercise of stock options, shares	257					257
Issuance of shares under employee stock purchase plan	$ 259							259
Issuance of shares under employee stock purchase plan, shares						23,209
Equity-based compensation	6,715							6,715
Equity-based compensation, shares						(1,191)
Net loss	(31,634)								(31,634)
Ending balance at Dec. 31, 2016	$ 209,837					$ 4		$ 263,403	$ (53,570)
Ending balance, shares at Dec. 31, 2016															0
Ending balance, shares at Dec. 31, 2016	36,018,540					36,018,540