CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenue:
Revenue	$ 144,419	$ 115,800
Expenses:
Research, development and patent	104,067	82,638
Selling, general and administrative	43,653	13,677
Total operating expenses	147,720	96,315
Income (loss) from operations	(3,301)	19,485
Other income (expense):
Investment income	3,610	2,280
Interest expense	(10,938)	(11,363)
Other expenses	(168)	(1,438)
Income (loss) before income tax expense	(10,797)	8,964
Income tax expense	(15)	0
Net income (loss)	(10,812)	8,964
Net loss attributable to noncontrolling interest in Akcea Therapeutics, Inc.	9,392	0
Net income (loss) attributable to Ionis Pharmaceuticals, Inc. common stockholders	$ (1,420)	$ 8,964
Basic net income (loss) per share (in dollars per share)	$ (0.01)	$ 0.07
Shares used in computing basic net income (loss) per share (in shares)	125,330	122,861
Diluted net income (loss) per share (in dollars per share)	$ (0.01)	$ 0.07
Shares used in computing diluted net income (loss) per share (in shares)	125,330	124,972
Commercial Revenue [Member]
Revenue:
Revenue	$ 42,023	$ 7,801
SPINRAZA Royalties [Member]
Revenue:
Revenue	41,081	5,211
Licensing and Other Royalty Revenue [Member]
Revenue:
Revenue	942	2,590
Research and Development Under Collaborative Agreements [Member]
Revenue:
Revenue	$ 102,396	$ 107,999