Condensed Consolidated Statement of Shareholders' (Deficit) 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	NovaQuest Private Placement	NovaQuest Private Placement Common Shares	NovaQuest 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]
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 from former majority shareholder — 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	(198,537)
Ending balance (in shares) at Dec. 31, 2018		70,801,521
Ending balance at Dec. 31, 2018	46,735	$ 1	473,518	227	(427,011)
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]
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 from former majority shareholder — share-based compensation	196		196
Capital contribution from former majority shareholder	212		212
Foreign currency translation adjustment	(72)			(72)
Issuance of shares upon exercise of stock options and vesting of PSUs and RSUs (in shares)		60,271
Issuance of shares upon exercise of stock options and vesting of PSUs and 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)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of shares (in shares)																2,286,284
Issuance of shares															$ 37,982		$ 37,982
Share-based compensation expense	4,669		4,669
Capital contribution from former majority shareholder — share-based compensation	125		125
Capital contribution from former majority shareholder	384		384
Foreign currency translation adjustment	(150)			(150)
Issuance of shares upon exercise of stock options and vesting of PSUs and RSUs (in shares)		30,349
Issuance of shares upon exercise of stock options and vesting of PSUs and RSUs	257		257
Net loss	(70,633)				(70,633)
Ending balance (in shares) at Dec. 31, 2018		70,801,521
Ending balance at Dec. 31, 2018	$ 46,735	$ 1	473,518	227	(427,011)
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 (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 from former majority shareholder — share-based compensation	42		42
Capital contribution from former majority shareholder	106		106
Foreign currency translation adjustment	(819)			(819)
Issuance of shares upon exercise of stock options and vesting of PSUs and RSUs (in shares)		34,399
Issuance of shares upon exercise of stock options and vesting of PSUs and 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)	80,548
Net loss	$ (224,076)
Ending balance (in shares) at Dec. 31, 2019	89,787,654	89,787,654
Ending balance at Dec. 31, 2019	$ (48,888)	$ 2	678,034	(823)	(726,101)
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]
Issuance of shares (in shares)							0
Issuance of shares						$ (80)	$ 0	$ (80)
Share-based compensation expense	7,879		7,879
Capital contribution from former majority shareholder — share-based compensation	52		52
Capital contribution from former majority shareholder	123		123
Foreign currency translation adjustment	281			281
Issuance of shares upon exercise of stock options and vesting of PSUs and RSUs (in shares)		938
Issuance of shares upon exercise of stock options and vesting of PSUs and RSUs	0		0
Net loss	(70,568)				(70,568)
Ending balance (in shares) at Sep. 30, 2019		89,623,564
Ending balance at Sep. 30, 2019	17,254	$ 2	657,780	(31)	(640,497)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation expense	19,740		19,740
Capital contribution from former majority shareholder — share-based compensation	55		55
Capital contribution from former majority shareholder	105		105
Foreign currency translation adjustment	(792)			(792)
Issuance of shares upon exercise of stock options and vesting of PSUs and RSUs (in shares)		164,090
Issuance of shares upon exercise of stock options and vesting of PSUs and RSUs	354		354
Net loss	$ (85,604)				(85,604)
Ending balance (in shares) at Dec. 31, 2019	89,787,654	89,787,654
Ending balance at Dec. 31, 2019	$ (48,888)	$ 2	$ 678,034	$ (823)	$ (726,101)