Supplemental Financial Statements Information - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021	[1]
Inventory [Line Items]
Inventory	$ 802,315		$ 802,315		$ 776,669
Depreciation expense, net of amounts capitalized into inventory	9,500	$ 11,800	21,200	$ 24,300
Gain on sale of nonfinancial assets, net	0	$ 0	108,000	$ 0
Valoctocogene Roxaparvovec
Inventory [Line Items]
Inventory	$ 31,800		$ 31,800

[1] (1)December 31, 2021 balances were derived from the audited Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2021, filed with the SEC on February 25, 2022.