CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenue:
Revenue	$ 133,093	$ 160,079	$ 370,450	$ 438,983
Expenses:
Cost of sales	3,079	3,086	8,616	8,646
Research, development and patent	184,770	125,083	463,878	364,298
Selling, general and administrative	31,093	68,447	148,747	215,455
Total operating expenses	218,942	196,616	621,241	588,399
Loss from operations	(85,849)	(36,537)	(250,791)	(149,416)
Other income (expense):
Investment income	872	6,454	8,236	25,913
Interest expense	(2,340)	(2,428)	(7,111)	(7,076)
Gain on investments	4,013	835	4,885	10,722
Loss on early retirement of debt	0	0	(8,627)	0
Other income (expenses)	(469)	126	(656)	(122)
Loss before income tax benefit (expense)	(83,773)	(31,550)	(254,064)	(119,979)
Income tax benefit (expense)	1,307	(5,064)	854	(4,077)
Net loss	(82,466)	(36,614)	(253,210)	(124,056)
Net loss attributable to noncontrolling interest in Akcea Therapeutics, Inc.	0	12,147	0	34,325
Net loss attributable to Ionis Pharmaceuticals, Inc. common stockholders	$ (82,466)	$ (24,467)	$ (253,210)	$ (89,731)
Basic net loss per share (in dollars per share)	$ (0.58)	$ (0.18)	$ (1.80)	$ (0.64)
Diluted net loss per share (in dollars per share)	$ (0.58)	$ (0.18)	$ (1.80)	$ (0.64)
Shares used in computing basic net loss per share (in shares)	141,139	139,708	140,958	139,497
Shares used in computing diluted net loss per share (in shares)	141,139	139,708	140,958	139,497
Commercial Revenue [Member]
Revenue:
Revenue	$ 84,820	$ 95,340	$ 255,129	$ 269,035
SPINRAZA Royalties [Member]
Revenue:
Revenue	66,572	74,171	198,726	211,925
TEGSEDI and WAYLIVRA Revenue, Net [Member]
Revenue:
Revenue	15,519	19,040	46,901	50,562
Licensing and Other Royalty Revenue [Member]
Revenue:
Revenue	2,729	2,129	9,502	6,548
Research and Development Revenue Under Collaborative Agreements [Member]
Revenue:
Revenue	$ 48,273	$ 64,739	$ 115,321	$ 169,948