Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2018
Summary Of Significant Accounting Policies [Line Items]
Description of significant off-balance sheet risk	The Company has no significant off-balance sheet risk, such as foreign currency contracts, options contracts, or other foreign hedging arrangements.
Foreign currency transaction gain (loss)	$ (24,300,000)	$ (1,200,000)
Outstanding letter of credit associated with a lease	3,000,000.0	3,000,000.0
Cash collateral associated with corporate credit cards and other leases	1,300,000	1,300,000
Credit losses related to outstanding accounts receivable	$ 0	0
Change in accounting principle, accounting standards update, adopted	true
Change in accounting principle, accounting standards update, adoption date	Jan. 01, 2022
New accounting pronouncement or change in accounting principle, description	ASU No. 2021-10
Change in accounting principle, accounting standards update, immaterial effect	true
Property and equipment	$ 8,138,000	4,767,000
Right-of-use assets	$ 22,774,000	24,316,000
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
Strimvelis
Summary Of Significant Accounting Policies [Line Items]
Liability associated with the loss contract			$ 18,400,000
Strimvelis loss provision current		700,000
Strimvelis loss provision non current		2,700,000
Libmeldy | Minimum
Summary Of Significant Accounting Policies [Line Items]
General payment terms	30 days
Libmeldy | Maximum
Summary Of Significant Accounting Policies [Line Items]
General payment terms	1 year
United Kingdom
Summary Of Significant Accounting Policies [Line Items]
Property and equipment	$ 7,500,000	3,600,000
Right-of-use assets	11,600,000
US
Summary Of Significant Accounting Policies [Line Items]
Property and equipment	600,000	1,200,000
Right-of-use assets	$ 11,200,000	12,500,000
United Kingdom and European Union
Summary Of Significant Accounting Policies [Line Items]
Right-of-use assets		$ 11,800,000