CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenue:
Revenue	$ 117,747	$ 112,273	$ 262,165	$ 228,073
Expenses:
Research, development and patent	101,830	83,506	205,897	166,144
Selling, general and administrative	66,198	22,317	109,851	35,994
Total operating expenses	168,028	105,823	315,748	202,138
Income (loss) from operations	(50,281)	6,450	(53,583)	25,935
Other income (expense):
Investment income	5,134	2,465	8,748	4,744
Interest expense	(11,113)	(11,778)	(22,051)	(23,141)
Other income (expenses)	45	0	(123)	(1,438)
Income (loss) before income tax expense	(56,215)	(2,863)	(67,009)	6,100
Income tax expense	(358)	(222)	(372)	(222)
Net income (loss)	(56,573)	(3,085)	(67,381)	5,878
Net loss attributable to noncontrolling interest in Akcea Therapeutics, Inc.	16,215	0	25,606	0
Net income (loss) attributable to Ionis Pharmaceuticals, Inc. common stockholders	$ (40,358)	$ (3,085)	$ (41,775)	$ 5,878
Basic net income (loss) per share (in dollars per share)	$ (0.29)	$ (0.02)	$ (0.30)	$ 0.05
Shares used in computing basic net income (loss) per share (in shares)	128,712	123,989	127,030	123,428
Diluted net income (loss) per share (in dollars per share)	$ (0.29)	$ (0.02)	$ (0.30)	$ 0.05
Shares used in computing diluted net income (loss) per share (in shares)	128,712	123,989	127,030	125,511
Commercial Revenue [Member]
Revenue:
Revenue	$ 57,198	$ 23,688	$ 99,221	$ 31,489
SPINRAZA Royalties [Member]
Revenue:
Revenue	56,653	22,366	97,734	27,577
Licensing and Other Royalty Revenue [Member]
Revenue:
Revenue	545	1,322	1,487	3,912
Research and Development Revenue Under Collaborative Agreements [Member]
Revenue:
Revenue	$ 60,549	$ 88,585	$ 162,944	$ 196,584