Significant Accounting Policies, Cost of Products Sold (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2019
Cost of Products Sold [Abstract]
Previously expensed costs to produce TEGSEDI related to TEGSEDI commercial revenue	$ 0.2	$ 0.5

The costs related to goods produced and sold that were previously recognized as expense and are related to the commercial revenue recognized during the period.

No definition available.

Name:	ions_CostOfProductsSoldPreviouslyRecognized
Namespace Prefix:	ions_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration