Segment Information - Segment Information (Details) - Ionis Operations [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Segment Information [Abstract]
Revenue	$ 156,719	$ 133,814	$ 740,381	$ 478,562
Cost of sales	2,193	912	7,097	6,815
Drug discovery	28,412	25,790	85,656	80,652
Drug development	120,828	132,201	351,463	392,151
Medical affairs	8,874	5,511	22,342	17,279
Manufacturing and development chemistry	15,790	14,087	51,616	39,723
R&D support	23,092	20,052	64,252	59,065
Selling, general and administrative	86,565	51,933	234,626	153,083
Other segment items	(429)	23,808	75,322	79,342
Net loss	$ (128,606)	$ (140,480)	$ (151,993)	$ (349,548)