Basis of Presentation and Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	3 Months Ended	6 Months Ended		12 Months Ended
	Jun. 30, 2022	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021	Mar. 31, 2020	Dec. 31, 2018
Summary Of Significant Accounting Policies [Line Items]
Foreign currency transaction gain (loss)		$ (24,300,000)	$ 2,000,000.0
Tax incentive receivable, current	$ 11,226,000	11,226,000		$ 30,723,000
Proceeds from lines of credit		3,000,000.0		3,000,000.0
Cash collateral associated with corporate credit cards and other leases	1,300,000	1,300,000		1,300,000
Total revenue	$ 4,368,000	$ 9,892,000
Change in accounting principle, accounting standards update, adopted	true	true
Change in accounting principle, accounting standards update, adoption date	Jan. 01, 2022	Jan. 01, 2022
Change in accounting principle, accounting standards update, immaterial effect	true	true
New accounting pronouncement or change in accounting principle, description		ASU No. 2020-10
Accrued Expenses
Summary Of Significant Accounting Policies [Line Items]
Product revenue reserves	$ 0
Strimvelis
Summary Of Significant Accounting Policies [Line Items]
Total revenue	636,000	$ 636,000
Liability associated with the loss contract						$ 18,400,000
Strimvelis loss provision current	900,000	900,000
Strimvelis loss provision non-current	2,000,000.0	2,000,000.0
Libmeldy
Summary Of Significant Accounting Policies [Line Items]
Total revenue	3,145,000	8,204,000
Libmeldy | Government Rebates | Accrued Expenses
Summary Of Significant Accounting Policies [Line Items]
Product revenue reserves		$ 1,200,000
Minimum
Summary Of Significant Accounting Policies [Line Items]
General payment terms		30 days
Maximum
Summary Of Significant Accounting Policies [Line Items]
General payment terms		90 days
Fremont Lease Agreement [Member]
Summary Of Significant Accounting Policies [Line Items]
Escrow deposit	7,900,000	$ 7,900,000			$ 10,000,000.0
Increase decrease in escrow deposit		2,100,000
United Kingdom
Summary Of Significant Accounting Policies [Line Items]
Tax incentive receivable	15,200,000	15,200,000
Tax incentive receivable, current	$ 11,200,000	$ 11,200,000		$ 30,700,000