Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2023	Feb. 15, 2024	Jun. 30, 2023
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Annual Report	true
Document Period End Date	Dec. 31, 2023
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Document Transition Report	false
Entity File Number	000-19125
Entity Registrant Name	Ionis Pharmaceuticals, Inc
Entity Central Index Key	0000874015
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	33-0336973
Entity Address, Address Line One	2855 Gazelle Court
Entity Address, City or Town	Carlsbad
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92010
City Area Code	760
Local Phone Number	931-9200
Title of 12(b) Security	Common Stock, $.001 Par Value
Trading Symbol	IONS
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity Public Float			$ 4,243,321,410
Entity Common Stock, Shares Outstanding		145,751,797
Auditor Firm ID	42
Auditor Name	Ernst & Young LLP
Auditor Location	San Diego, California