Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Revenues [Abstract]
Revenue	$ 144,207	$ 159,767	$ 463,142	$ 435,478
Commercial Revenue [Member]
Revenues [Abstract]
Revenue	84,081	72,410	229,746	222,879
SPINRAZA Royalties [Member]
Revenues [Abstract]
Revenue	67,253	61,647	178,511	175,092
Other Commercial Revenue [Member]
Revenues [Abstract]
Revenue	16,828	10,763	51,235	47,787
TEGSEDI and WAYLIVRA Revenue, Net [Member]
Revenues [Abstract]
Revenue	8,286	5,920	25,420	22,467
Licensing and Other Royalty Revenue [Member]
Revenues [Abstract]
Revenue	8,542	4,843	25,815	25,320
Research and Development Revenue [Member]
Revenues [Abstract]
Revenue	60,126	87,357	233,396	212,599
Collaborative Agreement Revenue [Member]
Revenues [Abstract]
Revenue	44,167	69,250	173,513	157,282
Eplontersen Joint Development Revenue [Member]
Revenues [Abstract]
Revenue	$ 15,959	$ 18,107	$ 59,883	$ 55,317