Organization and Significant Accounting Policies, Cost of Products Sold (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Cost of Products Sold [Abstract]
Previously expensed costs to produce TEGSEDI related to TEGSEDI commercial revenue	$ 0.7	$ 0.1

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