Consolidated Statements of Changes in Redeemable Convertible Units, Redeemable Noncontrolling Interest, Stockholders' and Members' Deficit - USD ($) $ in Thousands	Total	TransTech Pharma, LLC (TTP) [Member]	Redeemable Convertible Preferred Units [Member]	Redeemable Convertible Preferred Units [Member] TransTech Pharma, LLC (TTP) [Member]	Redeemable Noncontrolling Interest [Member]	Class A Common Stock [Member]	Class B Common Stock [Member]	Members Deficit [Member]	Members Deficit [Member] TransTech Pharma, LLC (TTP) [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2014	$ (498,806)							$ (498,806)
Beginning balance, redeemable convertible preferred units at Dec. 31, 2014			$ 438,086
Net loss	(27,498)
Net loss prior to the Reorganization Transactions	(22,111)							(22,111)
Change in redemption value of TTP redeemable convertible preferred units		$ (75,077)		$ 75,077					$ (75,077)
Effect of Reorganization Transactions	596,244		$ (513,163)		$ (2,997)		$ 250	$ 595,994
Effect of Reorganization Transactions, shares							25,000,000
Issuance of Class A Common Stock in initial public offering, net of offering costs	104,445					$ 79				$ 104,366
Issuance of Class A Common Stock in initial public offering, net of offering costs, shares						7,812,500
Net loss subsequent to Reorganization Transactions	(5,387)				(13,609)						$ (5,387)
Share-based compensation	859									859
Exchange of Class B Common Stock for Class A Common Stock	12,461				(12,461)	$ 13	$ (13)			12,461
Exchange of Class B Common Stock for Class A Common Stock, shares						1,344,186	(1,344,186)
Change in redemption value of noncontrolling interest	(190,598)				190,598						(190,598)
Ending balance at Dec. 31, 2015	(77,970)					$ 92	$ 237			117,686	(195,985)
Ending balance, redeemable noncontrolling interest at Dec. 31, 2015					161,531
Ending balance, shares at Dec. 31, 2015						9,156,686	23,655,814
Net loss	(16,352)				(39,001)						(16,352)
Share-based compensation	2,641									2,641
Issuance of warrants to purchase Class A Common Stock	721									721
Exchange of Class B Common Stock for Class A Common Stock	3,164				(3,164)	$ 5	$ (5)			3,164
Exchange of Class B Common Stock for Class A Common Stock, shares						536,568	(536,568)
Change in redemption value of noncontrolling interest	(3,149)				3,149						(3,149)
Ending balance at Dec. 31, 2016	(90,945)					$ 97	$ 232			124,212	(215,486)
Ending balance, redeemable noncontrolling interest at Dec. 31, 2016	122,515				122,515
Ending balance, shares at Dec. 31, 2016						9,693,254	23,119,246
Net loss	(16,144)				(38,503)						(16,144)
Share-based compensation	3,645									3,645
Issuance of warrants to purchase Class A Common Stock	167									167
Issuance of Letter Agreement and warrants to purchase Class A Common Stock - related party	(342)									(342)
Change in redemption value of noncontrolling interest	(47,428)				47,428						(47,428)
Ending balance at Dec. 31, 2017	(151,047)					$ 97	$ 232			$ 127,682	$ (279,058)
Ending balance, redeemable noncontrolling interest at Dec. 31, 2017	$ 131,440				$ 131,440
Ending balance, shares at Dec. 31, 2017						9,693,254	23,119,246