Condensed Consolidated Statement of Shareholders' Equity - USD ($) $ in Thousands	Total	Common Shares	Additional Paid in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Public Offering	Public Offering Common Shares	Public Offering Additional Paid in Capital	Cowen and Company, LLC Private Placement	Cowen and Company, LLC Private Placement Common Shares	Cowen and Company, LLC Private Placement Additional Paid in Capital	Roivant Sciences, Ltd. Private Placement	Roivant Sciences, Ltd. Private Placement Common Shares	Roivant Sciences, Ltd. Private Placement Additional Paid in Capital
Beginning balance (in shares) at Mar. 31, 2018		60,997,856
Beginning balance at Mar. 31, 2018	$ 37,729	$ 1	$ 266,178	$ 24	$ (228,474)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Public equity offering, additional offering costs									$ (2,110)
Issuance of shares (in shares)										2,767,129			1,110,015
Issuance of shares									57,315		$ 57,315	$ 22,500		$ 22,500
Share-based compensation expense	4,053		4,053
Capital contribution — share-based compensation	191		191
Foreign currency translation adjustment	425			425
Issuance of shares upon exercise of stock options (in shares)		16,218
Issuance of shares upon exercise of stock options	76		76
Net loss	(62,134)				(62,134)
Ending balance (in shares) at Jun. 30, 2018		64,891,218
Ending balance at Jun. 30, 2018	60,155	$ 1	350,313	449	(290,608)
Beginning balance (in shares) at Mar. 31, 2018		60,997,856
Beginning balance at Mar. 31, 2018	37,729	$ 1	266,178	24	(228,474)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(127,904)
Ending balance (in shares) at Sep. 30, 2018		68,484,888
Ending balance at Sep. 30, 2018	74,101	$ 1	430,101	377	(356,378)
Beginning balance (in shares) at Jun. 30, 2018		64,891,218
Beginning balance at Jun. 30, 2018	60,155	$ 1	350,313	449	(290,608)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Public equity offering, additional offering costs						$ (5,110)
Issuance of shares (in shares)							3,533,399
Issuance of shares						74,391		$ 74,391
Share-based compensation expense	4,529		4,529
Capital contribution — share-based compensation	196		196
Capital contribution from RSI and RSG	212		212
Foreign currency translation adjustment	(72)			(72)
Issuance of shares upon exercise of stock options and vesting of RSUs (in shares)		60,271
Issuance of shares upon exercise of stock options and vesting of RSUs	460		460
Net loss	(65,770)				(65,770)
Ending balance (in shares) at Sep. 30, 2018		68,484,888
Ending balance at Sep. 30, 2018	$ 74,101	$ 1	430,101	377	(356,378)
Beginning balance (in shares) at Mar. 31, 2019	72,057,490	72,057,490
Beginning balance at Mar. 31, 2019	$ 4,334	$ 1	505,851	507	(502,025)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Public equity offering, additional offering costs						(9,229)			(79)
Issuance of shares (in shares)							17,424,243			106,494
Issuance of shares						$ 134,538	$ 1	$ 134,537	$ 2,546		$ 2,546
Share-based compensation expense	6,410		6,410
Capital contribution — share-based compensation	42		42
Capital contribution from RSI and RSG	106		106
Foreign currency translation adjustment	(819)			(819)
Issuance of shares upon exercise of stock options and vesting of RSUs (in shares)		34,399
Issuance of shares upon exercise of stock options and vesting of RSUs	314		314
Net loss	(67,904)				(67,904)
Ending balance (in shares) at Jun. 30, 2019		89,622,626
Ending balance at Jun. 30, 2019	$ 79,567	$ 2	649,806	(312)	(569,929)
Beginning balance (in shares) at Mar. 31, 2019	72,057,490	72,057,490
Beginning balance at Mar. 31, 2019	$ 4,334	$ 1	505,851	507	(502,025)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of shares upon exercise of stock options (in shares)	33,461
Net loss	$ (138,472)
Ending balance (in shares) at Sep. 30, 2019	89,623,564	89,623,564
Ending balance at Sep. 30, 2019	$ 17,254	$ 2	657,780	(31)	(640,497)
Beginning balance (in shares) at Jun. 30, 2019		89,622,626
Beginning balance at Jun. 30, 2019	79,567	$ 2	649,806	(312)	(569,929)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Public equity offering, additional offering costs	(80)		(80)
Share-based compensation expense	7,879		7,879
Capital contribution — share-based compensation	52		52
Capital contribution from RSI and RSG	123		123
Foreign currency translation adjustment	281			281
Issuance of shares upon exercise of stock options and vesting of RSUs (in shares)		938
Issuance of shares upon exercise of stock options and vesting of RSUs	0
Net loss	$ (70,568)				(70,568)
Ending balance (in shares) at Sep. 30, 2019	89,623,564	89,623,564
Ending balance at Sep. 30, 2019	$ 17,254	$ 2	$ 657,780	$ (31)	$ (640,497)