Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands		9 Months Ended
		Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities:
Net loss		$ (173,771)	$ (224,076)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Share-based compensation		21,746	34,178
Depreciation and amortization	[1]	1,787	1,236
Non-cash interest expense (2)	[2]	40	1,486
Loss on extinguishment of debt		0	4,851
Foreign currency transaction gain		(16,178)	(1,151)
Other		538	(23)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets		89	(1,892)
Income tax receivable		0	524
Other assets		(1,309)	(272)
Accounts payable		(2,977)	(4,402)
Interest payable		0	(1,077)
Interest payable (related party)		(15)	16
Accrued expenses		15,317	(8,521)
Change in deferred revenue		478,908	0
Cost share advance from collaboration partner		138,800	0
Operating lease liabilities		(1,112)	(547)
Deferred interest payable		0	(2,273)
Amounts due to related parties		628	0
Other liabilities		1,080	0
Net cash provided by (used in) operating activities		463,571	(201,943)
Cash flows from investing activities:
Purchases of marketable securities		(47,562)	(32,076)
Maturities of marketable securities		18,235	16,440
Purchases of property and equipment		(1,036)	(824)
Net cash used in investing activities		(30,363)	(16,460)
Cash flows from financing activities:
Proceeds from related party debt financing		200,000	113,700
Proceeds from stock option exercises		5,284	667
Payments on third party debt financings and redemption fees		0	(105,420)
Payment of annual debt administration fee to NovaQuest		0	(300)
Net cash provided by financing activities		205,284	145,651
Net change in cash, cash equivalents and restricted cash		638,492	(72,752)
Cash, cash equivalents and restricted cash, beginning of period		78,018	157,199
Cash, cash equivalents and restricted cash, end of period		716,510	84,447
Private Placement | Cowen and Company, LLC
Cash flows from financing activities:
Cash proceeds from issuance of common shares		0	2,546
Public Offering
Cash flows from financing activities:
Cash proceeds from issuance of common shares		$ 0	$ 134,458

[1] Includes amortization of operating lease right-of-use assets.

[2] Includes imputed interest on cost share advance from collaboration partner for the nine months ended December 31, 2020 and amortization of debt discount and issuance costs for the nine months ended December 31, 2019.