CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenue:
Revenue	$ 787,647	$ 587,367	$ 810,456
Expenses:
Cost of sales	9,133	14,116	10,842
Research, development and patent	899,625	833,147	643,453
Selling, general and administrative	232,619	150,295	186,347
Total operating expenses	1,141,377	997,558	840,642
Loss from operations	(353,730)	(410,191)	(30,186)
Other income (expense):
Investment income	89,041	25,331	10,044
Interest expense	(12,660)	(8,122)	(9,349)
Interest expense related to sale of future royalties	(68,797)	0	0
Gain (loss) on investments	(1,914)	(7,333)	10,103
Gain (loss) on sale of real estate assets	(161)	149,604	0
Other income (expense)	14,256	(7,274)	(9,760)
Loss before income tax benefit (expense)	(333,965)	(257,985)	(29,148)
Income tax benefit (expense)	(32,321)	(11,737)	551
Net loss	$ (366,286)	$ (269,722)	$ (28,597)
Basic net loss per share (in dollars per share)	$ (2.56)	$ (1.9)	$ (0.2)
Shares used in computing basic net loss per share (in shares)	143,190	141,848	141,021
Diluted net loss per share (in dollars per share)	$ (2.56)	$ (1.9)	$ (0.2)
Shares used in computing diluted net loss per share (in shares)	143,190	141,848	141,021
Commercial Revenue [Member]
Revenue:
Revenue	$ 308,591	$ 303,358	$ 342,395
SPINRAZA Royalties [Member]
Revenue:
Revenue	240,379	242,314	267,776
Other Commercial Revenue [Member]
Revenue:
Revenue	68,212	61,044	74,619
Research and Development Revenue [Member]
Revenue:
Revenue	479,056	284,009	468,061
Collaborative Agreement Revenue [Member]
Revenue:
Revenue	352,657	207,222	468,061
WAINUA Joint Development Revenue [Member]
Revenue:
Revenue	$ 126,399	$ 76,787	$ 0