Payments for capital contributions to a subsidiary.

No definition available.

Name:	ions_CapitalContributionToSubsidiary
Namespace Prefix:	ions_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The percentage of the subsidiary's results included in the company's financial statements.

+ References

No definition available.

+ Details

Name:	ions_PercentageOfResultsIncludedInConsolidation
Namespace Prefix:	ions_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The cash inflow associated with the amount received from entity's raising of capital via private rather than public placement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3255-108585

+ Details

Name:	us-gaap_ProceedsFromIssuanceOfPrivatePlacement
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The cash inflow from the issuance of common stock, preferred stock, treasury stock, stock options, and other types of equity.

+ References

+ Details

Name:	us-gaap_ProceedsFromIssuanceOrSaleOfEquity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- References

No definition available.

+ Details

Name:	us-gaap_ProceedsFromIssuanceOrSaleOfEquityAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Cash received on stock transaction after deduction of issuance costs.

+ References

No definition available.

+ Details

Name:	us-gaap_SaleOfStockConsiderationReceivedOnTransaction
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Percentage of subsidiary's or equity investee's stock owned by parent company after stock transaction.

+ References

No definition available.

+ Details

Name:	us-gaap_SaleOfStockPercentageOfOwnershipAfterTransaction
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of subsidiary's or equity investee's stock owned by parent company before stock transaction.

+ References

No definition available.

+ Details

Name:	us-gaap_SaleOfStockPercentageOfOwnershipBeforeTransaction
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	dei_LegalEntityAxis=ions_AkceaTherapeuticsIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Organization and Significant Accounting Policies, Noncontrolling Interest in Akcea Therapeutics, Inc. (Details) - USD ($) $ in Thousands	1 Months Ended	5 Months Ended	7 Months Ended	12 Months Ended
	Jul. 31, 2017	Dec. 31, 2017	Jul. 18, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Akcea IPO [Abstract]
Proceeds from sale of common stock to Novartis in a private placement				$ 50,000	$ 0	$ 0
Investment in subsidiary	$ 25,000
Percentage ownership before IPO			100.00%
Percentage of results included in consolidation			100.00%
Percentage ownership after IPO		68.00%
Akcea [Member]
Akcea IPO [Abstract]
Gross proceeds from IPO	193,800
Proceeds from sale of common stock to Novartis in a private placement	50,000
Net proceeds from IPO	$ 182,400