CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Revenue:
Revenue	$ 188,411	$ 133,791	$ 318,935	$ 275,710
Expenses:
Cost of sales	2,537	4,745	3,880	8,914
Research, development and patent	229,927	180,758	427,740	341,884
Selling, general and administrative	46,142	33,802	91,658	67,929
Total operating expenses	278,606	219,305	523,278	418,727
Loss from operations	(90,195)	(85,514)	(204,343)	(143,017)
Other income (expense):
Investment income	20,792	3,403	39,419	5,396
Interest expense	(2,291)	(2,130)	(3,899)	(4,252)
Interest expense related to sale of future royalties	(17,655)	0	(33,170)	0
Gain (loss) on investments	718	(6,337)	189	(12,963)
Other income (expense)	11,183	(12,297)	11,414	(12,110)
Loss before income tax expense	(77,448)	(102,875)	(190,390)	(166,946)
Income tax expense	(7,842)	(2,260)	(19,223)	(3,354)
Net loss	$ (85,290)	$ (105,135)	$ (209,613)	$ (170,300)
Basic net loss per share (in dollars per share)	$ (0.6)	$ (0.74)	$ (1.47)	$ (1.2)
Diluted net loss per share (in dollars per share)	$ (0.6)	$ (0.74)	$ (1.47)	$ (1.2)
Shares used in computing basic net loss per share (in shares)	143,098	141,794	142,918	141,697
Shares used in computing diluted net loss per share (in shares)	143,098	141,794	142,918	141,697
Commercial Revenue [Member]
Revenue:
Revenue	$ 77,897	$ 78,184	$ 145,664	$ 150,468
SPINRAZA Royalties [Member]
Revenue:
Revenue	61,012	59,627	111,258	113,444
Other Commercial Revenue [Member]
Revenue:
Revenue	16,885	18,557	34,406	37,024
Research and Development Revenue [Member]
Revenue:
Revenue	110,514	55,607	173,271	125,242
Collaborative Agreement Revenue [Member]
Revenue:
Revenue	91,013	38,247	129,347	88,032
Eplontersen Joint Development Revenue [Member]
Revenue:
Revenue	$ 19,501	$ 17,360	$ 43,924	$ 37,210