CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Common Stock [Member]	Additional Paid In Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Deficit [Member]	Total Ionis Stockholders' Equity [Member]	Noncontrolling Interest in Akcea Therapeutics, Inc. [Member]	Total
Balance at Dec. 31, 2018	$ 138	$ 1,833,668	$ (32,016)	$ (840,251)	$ 961,539	$ 139,084	$ 1,100,623
Balance (in shares) at Dec. 31, 2018	137,929
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	$ 0	0	0	278,143	278,143	0	278,143
Change in unrealized gains (losses), net of tax	0	0	6,633	0	6,633	0	6,633
Foreign currency translation	0	0	93	0	93	0	93
Issuance of common stock in connection with employee stock plans	$ 3	119,654	0	0	119,657	0	119,657
Issuance of common stock in connection with employee stock plans (in shares)	3,100
Issuance of warrants	$ 0	56,110	0	0	56,110	0	56,110
Purchase of note hedges, net of tax	0	(85,860)	0	0	(85,860)	0	(85,860)
Repurchases and retirements of common stock	$ (1)	0	0	(34,387)	(34,388)	0	(34,388)
Repurchases and retirements of common stock (in shares)	(535)
Stock-based compensation expense	$ 0	146,574	0	0	146,574	0	146,574
Payments of tax withholdings related to vesting of employee stock awards and exercise of employee stock options	$ 0	(19,242)	0	0	(19,242)	0	(19,242)
Payments of tax withholdings related to vesting of employee stock awards and exercise of employee stock options (in shares)	(154)
Noncontrolling interest in Akcea Therapeutics, Inc.	$ 0	(65,254)	0	0	(65,254)	74,370	9,116
Balance at Dec. 31, 2019	$ 140	1,985,650	(25,290)	(596,495)	1,364,005	213,454	1,577,459
Balance (in shares) at Dec. 31, 2019	140,340
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	$ 0	0	0	(444,263)	(444,263)	0	(444,263)
Change in unrealized gains (losses), net of tax	0	0	3,729	0	3,729	0	3,729
Foreign currency translation	0	0	617	0	617	0	617
Issuance of common stock in connection with employee stock plans	$ 1	52,033	0	0	52,034	0	52,034
Issuance of common stock in connection with employee stock plans (in shares)	1,721
Purchase of noncontrolling interest of Akcea Therapeutics, Inc., including cash payments for cancellation of Akcea Therapeutics, Inc. equity awards	$ 0	(324,022)	301	0	(323,721)	(220,965)	(544,686)
Repurchases and retirements of common stock	$ (1)	0	0	(90,548)	(90,549)	0	(90,549)
Repurchases and retirements of common stock (in shares)	(1,478)
Stock-based compensation expense	$ 0	230,117	0	0	230,117	0	230,117
Payments of tax withholdings related to vesting of employee stock awards and exercise of employee stock options	$ 0	(13,410)	0	0	(13,410)	0	(13,410)
Payments of tax withholdings related to vesting of employee stock awards and exercise of employee stock options (in shares)	(217)
Deferred tax liability adjustment due to purchase of noncontrolling interest of Akcea Therapeutics, Inc.	$ 0	7,714	0	0	7,714	0	7,714
Noncontrolling interest in Akcea Therapeutics, Inc.	0	(42,563)	(428)	0	(42,991)	7,511	(35,480)
Balance at Dec. 31, 2020	$ 140	1,895,519	(21,071)	(1,131,306)	743,282	0	743,282
Balance (in shares) at Dec. 31, 2020	140,366
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	$ 0	0	0	(28,597)	(28,597)	0	(28,597)
Change in unrealized gains (losses), net of tax	0	0	(11,486)	0	(11,486)	0	(11,486)
Foreign currency translation	0	0	(111)	0	(111)	0	(111)
Issuance of common stock in connection with employee stock plans	$ 1	11,563	0	0	11,564	0	11,564
Issuance of common stock in connection with employee stock plans (in shares)	1,132
Issuance of warrants	$ 0	89,752	0	0	89,752	0	89,752
Purchase of note hedges, net of tax	0	(136,620)	0	0	(136,620)	0	(136,620)
Stock-based compensation expense	0	120,678	0	0	120,678	0	120,678
Payments of tax withholdings related to vesting of employee stock awards and exercise of employee stock options	$ 0	(16,725)	0	0	(16,725)	0	(16,725)
Payments of tax withholdings related to vesting of employee stock awards and exercise of employee stock options (in shares)	(288)
Balance at Dec. 31, 2021	$ 141	$ 1,964,167	$ (32,668)	$ (1,159,903)	$ 771,737	$ 0	$ 771,737
Balance (in shares) at Dec. 31, 2021	141,210