CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenue:
Revenue	$ 297,214	$ 144,419
Expenses:
Cost of products sold	1,041	0
Research, development and patent	106,417	104,067
Selling, general and administrative	68,221	43,653
Total operating expenses	175,679	147,720
Income (loss) from operations	121,535	(3,301)
Other income (expense):
Investment income	12,142	3,610
Interest expense	(11,599)	(10,938)
Other expenses	(147)	(168)
Income (loss) before income tax expense	121,931	(10,797)
Income tax expense	(31,047)	(15)
Net income (loss)	90,884	(10,812)
Net (income) loss attributable to noncontrolling interest in Akcea Therapeutics, Inc.	(6,441)	9,392
Net income (loss) attributable to Ionis Pharmaceuticals, Inc. common stockholders	$ 84,443	$ (1,420)
Basic net income (loss) per share (in dollars per share)	$ 0.63	$ (0.01)
Shares used in computing basic net income (loss) per share (in shares)	138,582	125,330
Diluted net income (loss) per share (in dollars per share)	$ 0.62	$ (0.01)
Shares used in computing diluted net income (loss) per share (in shares)	141,537	125,330
Commercial Revenue [Member]
Revenue:
Revenue	$ 68,088	$ 42,023
SPINRAZA Royalties [Member]
Revenue:
Revenue	59,711	41,081
TEGSEDI Product Sales, Net [Member]
Revenue:
Revenue	6,754	0
Licensing and Other Royalty Revenue [Member]
Revenue:
Revenue	1,623	942
Research and Development Revenue Under Collaborative Agreements [Member]
Revenue:
Revenue	$ 229,126	$ 102,396