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
Foreign currency translation adjustment	0
Net loss	(1,657)					(1,657)
Ending balance (in shares) at Mar. 31, 2016		37,231,342
Ending balance at Mar. 31, 2016	(223)	$ 1	(1)	1,434	0	(1,657)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued (in shares)		14,500,000
Shares issued	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 Takeda warrant liability (in shares)	2,339,192	2,339,192
Shares issued to settle the Takeda warrant liability	$ 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
Foreign currency 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)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adjustment to adopt ASU 2016-09	0			122		(122)
Shares issued (in shares)		138,361
Shares issued	1,857	$ 0		1,857
Shares issued to settle the Takeda warrant liability (in shares)		4,432
Shares issued to settle the Takeda warrant liability	58	$ 0		58
Share-based compensation expense (in shares)		564,111
Share-based compensation expense	10,587	$ 0		10,587
Capital contribution — share-based compensation	996			996
Foreign currency translation adjustment	$ (116)				(116)
Stock option exercises (in shares)	15,195	15,195
Stock option exercises	$ 36	$ 0		36
Warrants issued to Hercules with long-term debt	789			789
Settlement of Roivant Sciences Ltd. common shares subscribed	1		1
Net loss	$ (143,255)					(143,255)
Ending balance (in shares) at Mar. 31, 2018	60,997,856	60,997,856
Ending balance at Mar. 31, 2018	$ 37,729	$ 1	$ 0	$ 266,178	$ 24	$ (228,474)