CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Unaudited) [Abstract]
Net income (loss)	$ (58,480)	$ 90,884
Unrealized gains (losses) on debt securities, net of tax	(1,954)	4,324
Currency translation adjustment	9	84
Comprehensive income (loss)	(60,425)	95,292
Comprehensive (income) loss attributable to noncontrolling interests	(10,254)	6,441
Comprehensive income (loss) attributable to Ionis Pharmaceuticals, Inc. stockholders	$ (50,171)	$ 88,851