CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenue:
Revenue	$ 160,079	$ 167,892	$ 438,983	$ 628,918
Expenses:
Cost of products sold	3,086	967	8,646	3,373
Research, development and patent	125,083	104,366	364,298	316,948
Selling, general and administrative	68,447	60,036	215,455	203,368
Total operating expenses	196,616	165,369	588,399	523,689
Income (loss) from operations	(36,537)	2,523	(149,416)	105,229
Other income (expense):
Investment income	6,454	13,136	25,913	39,015
Interest expense	(11,321)	(12,002)	(33,484)	(35,404)
Gain on investments	835	0	10,722	0
Other income (expenses)	126	(140)	(122)	(332)
Income (loss) before income tax (expense) benefit	(40,443)	3,517	(146,387)	108,508
Income tax (expense) benefit	(2,648)	14,915	1,047	(9,204)
Net income (loss)	(43,091)	18,432	(145,340)	99,304
Net loss attributable to noncontrolling interest in Akcea Therapeutics, Inc.	12,147	7,731	34,325	10,426
Net income (loss) attributable to Ionis Pharmaceuticals, Inc. common stockholders	$ (30,944)	$ 26,163	$ (111,015)	$ 109,730
Basic net income (loss) per share (in dollars per share)	$ (0.22)	$ 0.19	$ (0.80)	$ 0.81
Shares used in computing basic net income (loss) per share (in shares)	139,708	140,551	139,497	139,800
Diluted net income (loss) per share (in dollars per share)	$ (0.22)	$ 0.18	$ (0.80)	$ 0.79
Shares used in computing diluted net income (loss) per share (in shares)	139,708	143,408	139,497	142,821
Commercial Revenue [Member]
Revenue:
Revenue	$ 95,340	$ 95,699	$ 269,035	$ 252,085
SPINRAZA Royalties [Member]
Revenue:
Revenue	74,171	81,672	211,925	211,884
Product Sales, Net [Member]
Revenue:
Revenue	19,040	11,945	50,562	28,563
Licensing and Other Royalty Revenue [Member]
Revenue:
Revenue	2,129	2,082	6,548	11,638
Research and Development Revenue Under Collaborative Agreements [Member]
Revenue:
Revenue	$ 64,739	$ 72,193	$ 169,948	$ 376,833