CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue:
Revenue	$ 599,674	$ 514,179	$ 372,776
Expenses:
Cost of products sold	1,820	0	0
Research, development and patent	414,604	374,644	344,320
Selling, general and administrative	244,622	108,488	48,616
Total operating expenses	661,046	483,132	392,936
Income (loss) from operations	(61,372)	31,047	(20,160)
Other income (expense):
Investment income	30,187	8,179	5,472
Interest expense	(44,789)	(44,752)	(38,795)
Loss on extinguishment of financing liability for leased facility	0	(7,689)	0
Loss on early retirement of debt	0	0	(3,983)
Other expenses	(182)	(3,548)	0
Loss before income tax benefit (expense)	(76,156)	(16,763)	(57,466)
Income tax benefit (expense)	291,141	5,980	(2,934)
Net income (loss)	214,985	(10,783)	(60,400)
Net loss attributable to noncontrolling interest in Akcea Therapeutics, Inc.	58,756	11,129	0
Net income (loss) attributable to Ionis Pharmaceuticals, Inc. common stockholders	$ 273,741	$ 346	$ (60,400)
Basic net income (loss) per share (in dollars per share)	$ 2.09	$ 0.15	$ (0.50)
Shares used in computing basic net income (loss) per share (in shares)	132,320	124,016	120,933
Diluted net income (loss) per share (in dollars per share)	$ 2.07	$ 0.15	$ (0.50)
Shares used in computing diluted net income (loss) per share (in shares)	134,056	126,098	120,933
Commercial Revenue [Member]
Revenue:
Revenue	$ 254,922	$ 120,014	$ 22,767
SPINRAZA Royalties [Member]
Revenue:
Revenue	237,930	112,540	883
TEGSEDI Product Sales, Net [Member]
Revenue:
Revenue	2,237	0	0
Licensing and Other Royalty Revenue [Member]
Revenue:
Revenue	14,755	7,474	21,884
Research and Development Revenue Under Collaborative Agreements [Member]
Revenue:
Revenue	$ 344,752	$ 394,165	$ 350,009