The number of agreements entered into with the collaboration partner.

No definition available.

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

- Definition

The amount of payments received during the period for advancing programs under the collaboration agreement.

+ References

No definition available.

+ Details

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

- Definition

The time period between billing a collaboration partner for goods delivered or services performed that are due unconditionally and payment is received from the collaboration partner, 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_PeriodAfterBillingWhenPaymentIsReceived
Namespace Prefix:	ions_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of separate performance obligations under the collaboration agreement.

+ References

No definition available.

+ Details

Name:	ions_RevenueFromContractWithCustomerNumberOfSeparatePerformanceObligations
Namespace Prefix:	ions_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

The amount of consideration the Company is eligible to earn under the collaboration agreement, including any variable consideration.

+ References

No definition available.

+ Details

Name:	ions_RevenueFromContractWithCustomerTransactionPrice
Namespace Prefix:	ions_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The additional amount of consideration the Company earned under the collaboration agreement that is added to the transaction price.

+ References

No definition available.

+ Details

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

- Definition

The amount of upfront payments received during the period under the collaboration agreement.

+ References

No definition available.

+ Details

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

- References

No definition available.

+ Details

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

- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130543-203045

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130539-203045

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130545-203045

+ Details

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

- Details

Name:	srt_MajorCustomersAxis=ions_BiogenIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ProductOrServiceAxis=ions_LicensingAndOtherRoyaltiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ProductOrServiceAxis=ions_ResearchAndDevelopmentRevenueUnderCollaborativeAgreementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=ions_CollaborativeArrangementAndLicensingAgreementEnteredIntoInApril2013WithRocheMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=ions_CollaborativeArrangementAndLicensingAgreementEnteredIntoInOctober2018WithRocheMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=ions_CollaborativeArrangementAndLicensingAgreementEnteredIntoInDecember2012WithBiogenMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=ions_CollaborativeArrangementAndLicensingAgreementEnteredIntoInJuly2015WithAstraZenecaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=ions_CollaborativeArrangementAndLicensingAgreementEnteredIntoInSeptember2013WithBiogenMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=ions_CollaborativeArrangementsAndLicensingAgreementsBayerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=ions_CollaborativeArrangementAndLicensingAgreementEnteredIntoInMay2015WithBayerMember
Namespace Prefix:
Data Type:	na
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Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=ions_CollaborativeArrangementAndLicensingAgreementAmendedInFebruary2017WithBayerMember
Namespace Prefix:
Data Type:	na
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Organization and Significant Accounting Policies, Revenue Recognition - Revenue Sources (Details) $ in Thousands	1 Months Ended							2 Months Ended	3 Months Ended					12 Months Ended
	Oct. 31, 2018 USD ($) PerformanceObligation	Feb. 28, 2017 USD ($) PerformanceObligation	Jul. 31, 2015 USD ($) PerformanceObligation	May 31, 2015 USD ($) PerformanceObligation	Sep. 30, 2013 USD ($) PerformanceObligation	Apr. 30, 2013 USD ($) PerformanceObligation	Dec. 31, 2012 USD ($) PerformanceObligation	Mar. 01, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 Agreement	Sep. 30, 2017 USD ($)	Jun. 30, 2015 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Revenue Recognition [Abstract]
Revenue				$ 91,200										$ 599,674	$ 514,179	$ 372,776
Period of time after billing when payment is received														3 months
Biogen [Member]
Revenue Recognition [Abstract]
Number of agreements \| Agreement											2
Licensing and Other Royalties [Member]
Revenue Recognition [Abstract]
Revenue														$ 14,755	7,474	21,884
R&D [Member]
Revenue Recognition [Abstract]
Revenue														344,752	394,165	350,009
Huntington's Disease [Member]
Revenue Recognition [Abstract]
Upfront payment received						$ 30,000
Number of separate performance obligations \| PerformanceObligation						1
Transaction price						$ 30,000
Huntington's Disease [Member] \| Subsequent Event [Member]
Revenue Recognition [Abstract]
Upfront payment received								$ 35,000
IONIS-FB-L for Complement-Mediated Diseases [Member]
Revenue Recognition [Abstract]
Upfront payment received	$ 75,000								$ 75,000
Number of separate performance obligations \| PerformanceObligation	1
Transaction price	$ 75,000
Neurology [Member]
Revenue Recognition [Abstract]
Upfront payment received							$ 30,000
Milestone payments received and added to transaction price												$ 10,000
Number of separate performance obligations \| PerformanceObligation							1
Transaction price							$ 30,000
Cardiac, Renal and Metabolic Diseases [Member]
Revenue Recognition [Abstract]
Upfront payment received			$ 65,000
Revenue										$ 10,000
Number of separate performance obligations \| PerformanceObligation			1
Transaction price			$ 65,000
Cardiac, Renal and Metabolic Diseases [Member] \| R&D [Member]
Revenue Recognition [Abstract]
Revenue										10,000
2013 Strategic Neurology [Member]
Revenue Recognition [Abstract]
Upfront payment received					$ 100,000
Revenue										$ 10,000
Number of separate performance obligations \| PerformanceObligation					1
Transaction price					$ 100,000
2013 Strategic Neurology [Member] \| Licensing and Other Royalties [Member]
Revenue Recognition [Abstract]
Revenue									35,000
2013 Strategic Neurology [Member] \| R&D [Member]
Revenue Recognition [Abstract]
Revenue									$ 5,000
Bayer [Member] \| R&D [Member]
Revenue Recognition [Abstract]
Revenue														$ 5,000	$ 67,100	$ 5,400
Bayer [Member]
Revenue Recognition [Abstract]
Upfront payment received				$ 100,000									$ 100,000
Number of separate performance obligations \| PerformanceObligation				3
Transaction price				$ 100,000
Bayer [Member]
Revenue Recognition [Abstract]
Payment received for advancing programs		$ 75,000
Number of separate performance obligations \| PerformanceObligation		3
Transaction price		$ 75,000