CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) [Abstract]
Net income (loss)	$ (10,812)	$ 8,964
Unrealized gains (losses) on debt securities, net of tax	(1,530)	266
Reclassification adjustment for realized gains included in net income (loss)	0	(374)
Currency translation adjustment	55	(6)
Comprehensive income (loss)	(12,287)	8,850
Comprehensive loss attributable to noncontrolling interests	9,423	0
Comprehensive income (loss) attributable to Ionis Pharmaceuticals, Inc. stockholders	$ (2,864)	$ 8,850