Revenues (Details) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	Dec. 31, 2021 USD ($) Component PerformanceObligation
Revenues [Abstract]
Revenue	$ 225,250	$ 188,411	$ 344,748	$ 318,935
WAINUA (Eplontersen) Collaboration with AstraZeneca [Member]
Revenues [Abstract]
Upfront payment received					$ 200,000
Number of material components | Component					4
Number of performance obligations | PerformanceObligation					1
Transaction price					$ 200,000
Percentage of costs associated with ongoing global Phase 3 development program paid by AstraZeneca			55.00%
Commercial Revenue [Member]
Revenues [Abstract]
Revenue	72,036	77,897	$ 131,629	145,664
SPINRAZA Royalties [Member]
Revenues [Abstract]
Revenue	56,743	61,012	95,198	111,258
WAINUA Royalties [Member]
Revenues [Abstract]
Revenue	3,781	0	4,907	0
Other Commercial Revenue [Member]
Revenues [Abstract]
Revenue	11,512	16,885	31,524	34,406
TEGSEDI and WAYLIVRA Revenue, Net [Member]
Revenues [Abstract]
Revenue	8,192	10,655	16,820	17,133
Licensing and Other Royalty Revenue [Member]
Revenues [Abstract]
Revenue	3,320	6,230	14,704	17,273
Research and Development Revenue [Member]
Revenues [Abstract]
Revenue	153,214	110,514	213,119	173,271
Collaborative Agreement Revenue [Member]
Revenues [Abstract]
Revenue	141,524	91,013	190,870	129,347
WAINUA Joint Development Revenue [Member]
Revenues [Abstract]
Revenue	$ 11,690	$ 19,501	$ 22,249	$ 43,924