CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS [Abstract]
Net loss	$ (269,722)	$ (28,597)	$ (479,743)
Unrealized gains (losses) on investments, net of tax	(24,395)	(11,486)	3,729
Currency translation adjustment	(417)	(111)	617
Adjustments to other comprehensive loss from purchase of noncontrolling interest of Akcea Therapeutics, Inc.	0	0	(127)
Comprehensive loss	(294,534)	(40,194)	(475,524)
Comprehensive loss attributable to noncontrolling interest in Akcea Therapeutics, Inc.	0	0	(35,480)
Comprehensive loss attributable to Ionis Pharmaceuticals, Inc. common stockholders	$ (294,534)	$ (40,194)	$ (440,044)