Collaborative Arrangements and Licensing Agreements, External Project Funding (Details) $ in Millions	Dec. 31, 2018 USD ($)
Cystic Fibrosis Foundation [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Maximum amount of payments payable for regulatory and commercialization milestones	$ 18

The maximum amount of payments payable for regulatory and commercialization milestones under the collaboration agreement.

No definition available.

Name:	ions_MaximumAmountOfPaymentsPayableForRegulatoryAndCommercializationMilestones
Namespace Prefix:	ions_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant