Liability Related to Sale of Future Royalties -Schedule of Activity Within Liability Related to Sale of Future Royalties (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Liability Related To Sale Of Future Royalties [Line Items]
Proceeds from sale of future royalties in December 2020		$ 196,000
Current portion of liability related to sale of future royalties	$ (37,889)	(18,794)
Liability related to sale of future royalties	133,460	174,504
Royalty Agreements
Liability Related To Sale Of Future Royalties [Line Items]
Proceeds from sale of future royalties in December 2020		196,000
Deferred Transaction Cost		(3,473)
Interest expense recognized	26,277	771
Ending balance	171,349	$ 193,298
Zolgensma royalties paid to HCR	(48,226)
Current portion of liability related to sale of future royalties	(37,889)
Liability related to sale of future royalties	$ 133,460