Consolidated Statements of Shareholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Common Shares	Common Shares Subscribed	Additional Paid in Capital	Accumulated Other Comprehensive Income	Accumulated Deficit
Beginning balance (in shares) at Feb. 02, 2016		37,231,342
Beginning balance at Feb. 02, 2016	$ 0	$ 1	$ (1)	$ 0	$ 0	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Capital contribution	1,434			1,434
Translation adjustment	0
Net loss	$ (1,657)					(1,657)
Ending balance (in shares) at Mar. 31, 2016	37,231,342	37,231,342
Ending balance at Mar. 31, 2016	$ (223)	$ 1	(1)	1,434	0	(1,657)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Sale of common shares in initial public offering ($15.00 per share), net of underwriting discounts and commissions and offering expenses of $17,536 (in shares)		14,500,000
Sale of common shares in initial public offering ($15.00 per share), net of underwriting discounts and commissions and offering expenses of $17,536	199,964	$ 0		199,964
Shares issued to Takeda under the Takeda license agreement (in shares)		5,077,001
Shares issued to Takeda under the Takeda license agreement	$ 7,740	$ 0		7,740
Shares issued to settle the warrant liability to Takeda (in shares)	2,339,192	2,339,192
Shares issued to settle the warrant liability to Takeda	$ 32,843	$ 0		32,843
Share-based compensation expense (in shares)		1,128,222
Share-based compensation expense	3,775	$ 0		3,775
Capital contribution — share-based compensation	4,942			4,942
Capital contribution	1,035			1,035
Translation adjustment	140				140
Net loss	$ (83,440)					(83,440)
Ending balance (in shares) at Mar. 31, 2017	60,275,757	60,275,757
Ending balance at Mar. 31, 2017	$ 166,776	$ 1	$ (1)	$ 251,733	$ 140	$ (85,097)