Significant Accounting Policies, Cost of Products Sold (Details) $ in Millions	Mar. 31, 2019 USD ($)
Cost of Products Sold [Abstract]
Costs incurred to produce TEGSEDI that were previously recognized	$ 0.3

The cumulative costs related to goods produced and sold that were previously recognized as expense.

No definition available.

Name:	ions_CumulativeCostOfProductsSold
Namespace Prefix:	ions_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant