Segment Information - Segment Information (Details) - Ionis Operations [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Segment Information [Abstract]
Revenue	$ 452,049	$ 225,250	$ 583,660	$ 344,748
Cost of sales	3,541	3,951	4,904	5,903
Drug discovery	30,255	26,691	57,244	54,862
Drug development	117,689	134,199	230,635	259,951
Medical affairs	7,826	7,092	13,468	11,768
Manufacturing and development chemistry	21,545	14,195	35,826	25,636
R&D support	20,607	17,067	41,159	39,013
Selling, general and administrative	81,081	57,418	148,061	101,151
Other segment items	45,954	30,902	75,750	55,532
Net income (loss)	$ 123,551	$ (66,265)	$ (23,387)	$ (209,068)