Segment Information (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2024 USD ($) Segment	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Segment Information [Abstract]
Number of operating segments | Segment			1
Revenue			$ 705,138	$ 787,647	$ 587,367
Cost of sales			11,215	9,133	14,116
Selling, general and administrative			267,474	232,619	150,295
Net loss	$ (104,349)	$ (9,263)	$ (453,897)	(366,286)	(269,722)
Segment Reporting, Other Segment Item, Composition, Description			Other segment items include stock-based compensation expense, investment income, interest expense, gain or loss on investments, other income or expense and income tax expense or benefit.
Ionis Operations [Member]
Segment Information [Abstract]
Revenue			$ 705,138	787,647	587,367
Cost of sales			10,415	8,686	13,447
Drug discovery			114,350	125,649	181,302
Drug development			527,259	530,332	426,225
Medical affairs			27,229	19,454	15,948
Manufacturing and development chemistry			57,729	65,293	76,162
R&D support			82,559	81,019	59,840
Selling, general and administrative			230,478	205,135	124,370
Other segment items			109,016	118,365	(40,205)
Net loss			$ (453,897)	$ (366,286)	$ (269,722)