Collaborative Arrangements and Licensing Agreements, Roche (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2023 USD ($) PerformanceObligation Program Indication	Dec. 31, 2023 USD ($) PerformanceObligation Program Indication	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Oct. 31, 2018 PerformanceObligation	Dec. 31, 2013 USD ($) PerformanceObligation
Collaborative Arrangement and Licensing Agreement [Abstract]
Revenue		$ 787,647	$ 587,367	$ 810,456
Roche [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Revenue		48,838	67,202	$ 17,241
Deferred revenue	$ 36,700	$ 36,700	$ 22,400
Roche [Member] | Revenue [Member] | Strategic Partner [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Concentration percentage		6.00%	11.00%	2.00%
HD [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Maximum amount of payments receivable over term of collaboration	395,000	$ 395,000
Maximum amount of upfront payments over term of collaboration	30,000	30,000
Maximum amount of license fees over term of collaboration	45,000	45,000
Maximum amount of development milestone payments over term of collaboration	70,000	70,000
Maximum amount of regulatory milestone payments over term of collaboration	170,000	170,000
Maximum amount of sales milestone payments over term of collaboration	80,000	80,000
Maximum amount of milestone payments for each additional medicine successfully developed over term of collaboration	136,500	136,500
Cumulative payments received	150,000	150,000
Next payment to be achieved	17,500	17,500
Number of separate performance obligations | PerformanceObligation						1
Transaction price						$ 30,000
IONIS-FB-L for Complement-Mediated Diseases [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Maximum amount of payments receivable over term of collaboration	810,000	810,000
Maximum amount of upfront payments over term of collaboration	75,000	75,000
Maximum amount of license fees over term of collaboration	35,000	35,000
Maximum amount of development milestone payments over term of collaboration	145,000	145,000
Maximum amount of regulatory milestone payments over term of collaboration	279,000	279,000
Maximum amount of sales milestone payments over term of collaboration	280,000	280,000
Cumulative payments received	135,000	135,000
Next payment to be achieved	90,000	90,000
Number of separate performance obligations | PerformanceObligation					1
Cumulative payments included in transaction price for performance obligation	$ 97,000	$ 97,000
Milestone payments achieved and included in transaction price for performance obligation			$ 22,000
Number of disease indications | Indication	2	2
Royalty percentage received on net sales of medicine		20.00%
Revenue			$ 35,000
IONIS-FB-L for Complement-Mediated Diseases [Member] | GA [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Number of disease indications | Indication	1	1
IONIS-FB-L for Complement-Mediated Diseases [Member] | IgAN [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Number of disease indications | Indication	1	1
RNA-targeted Programs for AD and HD [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Maximum amount of payments receivable over term of collaboration	$ 625,000	$ 625,000
Upfront payment received	60,000
Maximum amount of development milestone payments over term of collaboration	167,000	167,000
Maximum amount of sales milestone payments over term of collaboration	398,000	398,000
Cumulative payments received	60,000	60,000
Next payment to be achieved	$ 7,500	$ 7,500
Number of early-stage programs | Program	2	2
Number of separate performance obligations | PerformanceObligation	2	2
Transaction price	$ 60,000	$ 60,000
RNA-targeted Programs for AD and HD [Member] | R&D Services for Investigational Medicine for AD [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Transaction price	45,000	45,000
RNA-targeted Programs for AD and HD [Member] | R&D Services for Investigational Medicine for HD [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Transaction price	$ 15,000	$ 15,000