CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Unaudited) [Abstract]
Net income (loss)	$ (43,769)	$ (10,012)	$ (102,249)	$ 80,873
Unrealized gains (losses) on debt securities, net of tax	11,204	3,452	9,251	7,775
Currency translation adjustment	74	(96)	82	(11)
Comprehensive income (loss)	(32,491)	(6,656)	(92,916)	88,637
Comprehensive loss attributable to noncontrolling interests	(11,441)	(9,136)	(21,695)	(2,696)
Comprehensive income (loss) attributable to Ionis Pharmaceuticals, Inc. stockholders	$ (21,050)	$ 2,480	$ (71,221)	$ 91,333