Fourth Quarter Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				12 Months Ended
	Dec. 31, 2023		Dec. 31, 2022		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Fourth Quarter Financial Data (Unaudited) [Abstract]
Revenue	$ 324,505	[1]	$ 151,890
Operating expenses	330,627	[2]	359,909		$ 1,141,377	$ 997,558	$ 840,642
Loss from operations	(6,122)		(208,019)		(353,730)	(410,191)	(30,186)
Net loss	$ (9,263)		$ (52,430)	[3]	$ (366,286)	$ (269,722)	$ (28,597)
Basic net loss per share (in dollars per share)	$ (0.06)	[4],[5]	$ (0.37)	[4],[5]	$ (2.56)	$ (1.9)	$ (0.2)
Diluted net loss per share (in dollars per share)	$ (0.06)	[4]	$ (0.37)	[4],[6]	$ (2.56)	$ (1.9)	$ (0.2)
Gain on sale of real estate assets			$ 150,100		$ (161)	$ 150,135	$ 0
WAINUA (Eplontersen) [Member]
Fourth Quarter Financial Data (Unaudited) [Abstract]
Revenue	$ 50,000
Cardiovascular, Renal and Metabolic Diseases [Member]
Fourth Quarter Financial Data (Unaudited) [Abstract]
Revenue	$ 36,000
Metagenomi License Agreement [Member]
Fourth Quarter Financial Data (Unaudited) [Abstract]
Upfront payment			$ 80,000

[1] Revenue was higher in the three months ended December 31, 2023 compared to the same period in 2022 primarily due to the $50 million milestone payment we earned from AstraZeneca when the FDA approved WAINUA for ATTRv-PN in the U.S., $36 million payment we earned when AstraZeneca licensed ION826 and revenue we recognized in the fourth quarter of 2023 from the upfront payments we received from our new collaborations with Otsuka, Roche and Novartis.

[2] Operating expenses were lower in the three months ended December 31, 2023 compared to the same period in 2022 primarily due to the $80 million upfront payment we made for our collaboration with Metagenomi in the fourth quarter of 2022.

[3] Our net loss for the three months ended December 31, 2022 includes the $150.1 million gain we recognized from the sale and leaseback transaction for our headquarters in Carlsbad, California.

[4] We compute net loss per share independently for each quarter during the year.

[5] As discussed in Note 1, Organization and Significant Accounting Policies, we compute basic net loss per share by dividing the total net loss by our weighted-average number of common shares outstanding during the period.

[6] We incurred a net loss for the fourth quarter of 2023 and 2022. As a result, we did not include dilutive common equivalent shares in the computation of diluted net loss per share because the effect would have been anti-dilutive.