CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Revenue:
Revenue	$ 133,791	$ 125,750	$ 275,710	$ 237,357
Expenses:
Cost of sales	4,745	2,958	8,914	5,537
Research, development and patent	180,758	139,306	341,884	279,107
Selling, general and administrative	33,802	56,455	67,929	117,653
Total operating expenses	219,305	198,719	418,727	402,297
Loss from operations	(85,514)	(72,969)	(143,017)	(164,940)
Other income (expense):
Investment income	3,403	2,734	5,396	7,364
Interest expense	(2,130)	(2,357)	(4,252)	(4,771)
Gain (loss) on investments	(6,337)	860	(12,963)	873
Other expense	(12,297)	(8,816)	(12,110)	(8,813)
Loss before income tax expense	(102,875)	(80,548)	(166,946)	(170,287)
Income tax expense	(2,260)	(327)	(3,354)	(457)
Net loss	$ (105,135)	$ (80,875)	$ (170,300)	$ (170,744)
Basic net loss per share (in dollars per share)	$ (0.74)	$ (0.57)	$ (1.20)	$ (1.21)
Diluted net loss per share (in dollars per share)	$ (0.74)	$ (0.57)	$ (1.20)	$ (1.21)
Shares used in computing basic net loss per share (in shares)	141,794	140,962	141,697	140,866
Shares used in computing diluted net loss per share (in shares)	141,794	140,962	141,697	140,866
Commercial Revenue [Member]
Revenue:
Revenue	$ 78,184	$ 85,861	$ 150,468	$ 170,309
SPINRAZA Royalties [Member]
Revenue:
Revenue	59,627	72,168	113,444	132,154
TEGSEDI and WAYLIVRA Revenue, Net [Member]
Revenue:
Revenue	10,386	11,544	16,547	31,382
Licensing and Other Royalty Revenue [Member]
Revenue:
Revenue	8,171	2,149	20,477	6,773
Research and Development Revenue [Member]
Revenue:
Revenue	55,607	39,889	125,242	67,048
Collaborative Agreement Revenue [Member]
Revenue:
Revenue	38,247	39,889	88,032	67,048
Eplontersen Joint Development Revenue [Member]
Revenue:
Revenue	$ 17,360	$ 0	$ 37,210	$ 0