The number of purchased facilities financed with mortgage debt.

No definition available.

Name:	ions_NumberOfPurchasedFacilitiesFinancedWithMortgageDebt
Namespace Prefix:	ions_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Period of time to make only payments of interest on the mortgage loan, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	ions_PeriodToMakeInterestOnlyPaymentsOnMortgageLoan
Namespace Prefix:	ions_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The cash outflow for acquisition of buildings (properties) whether for investment or use.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3213-108585

+ Details

Name:	us-gaap_PaymentsToAcquireBuildings
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- References

No definition available.

+ Details

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

- Details

Name:	us-gaap_DebtInstrumentAxis=ions_LongTermMortgageDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=ions_PrimaryResearchAndDevelopmentFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_ManufacturingFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Long-Term Obligations and Commitments, Research and Development and Manufacturing Facilities (Details) $ in Millions	1 Months Ended		12 Months Ended
	Jul. 31, 2017 USD ($)	Jul. 31, 2015 Facility	Dec. 31, 2020
Research and Development and Manufacturing Facilities [Abstract]
Number of purchased facilities financed with mortgage debt \| Facility		2
Long-term Mortgage Debt [Member]
Research and Development and Manufacturing Facilities [Abstract]
Face amount	$ 60.4
Primary R&D Facility [Member]
Research and Development and Manufacturing Facilities [Abstract]
Payment to acquire building	$ 79.4
Interest rate	3.88%
Period to make interest only payments on mortgage loan			5 years
Manufacturing Facility [Member]
Research and Development and Manufacturing Facilities [Abstract]
Payment to acquire building	$ 14.0
Interest rate	4.20%
Period to make interest only payments on mortgage loan			5 years