No definition available.

Name:	ions_CollaborativeArrangementAndLicensingAgreementAbstract
Namespace Prefix:	ions_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The license fee payment receivable per drug under the collaboration agreement.

+ References

No definition available.

+ Details

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

- Definition

The maximum amount of payments receivable for commercialization milestones under the collaboration agreement.

+ References

No definition available.

+ Details

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

- Definition

The maximum amount of payments receivable for development milestones under the collaboration agreement.

+ References

No definition available.

+ Details

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

- Definition

The maximum amount of payments receivable for milestones under the collaboration agreement.

+ References

No definition available.

+ Details

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

- Definition

The maximum amount of payments receivable for regulatory milestones under the collaboration agreement.

+ References

No definition available.

+ Details

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

- Definition

The number of drugs with an exclusive option that could be exercised to develop and commercialize the drug and a license fee is paid under the collaboration agreement. The collaboration partner will assume all further global development, regulatory and commercialization activities for the licensed drug.

+ References

No definition available.

+ Details

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

- Definition

The percentage of license fees, milestone payments and royalties paid as sublicense fee under the collaboration agreement.

+ References

No definition available.

+ Details

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

- Definition

The amount of the upfront payment received during the period under the collaboration agreement that was paid as a sublicense fee.

+ References

No definition available.

+ Details

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

- Definition

The amount of the upfront payment received during the period under the collaboration agreement that was retained by the entity.

+ References

No definition available.

+ Details

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

- Definition

The potential premium received if common stock is purchased in the future under a Stock Purchase Agreement (SPA) in conjunction with the collaboration agreement.

+ References

No definition available.

+ Details

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

- Definition

The total amount of the premium received over the trading price of common stock at the time of purchase.

+ References

No definition available.

+ Details

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

- Definition

The cash inflow from the sale of common stock, including the premium paid for the purchase of common stock.

+ References

No definition available.

+ Details

Name:	ions_ProceedsFromSaleOfCommonStockIncludingPremiumPaid
Namespace Prefix:	ions_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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

Royalty percentage received on the sales of a drug by a collaboration partner under the collaboration agreement.

+ References

No definition available.

+ Details

Name:	ions_RoyaltyPercentageReceivedOnSalesOfDrug
Namespace Prefix:	ions_
Data Type:	num:percentItemType
Balance Type:	na
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

- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=84177426&loc=d3e6351-108592

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13531-108611

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=84177426&loc=d3e6404-108592

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13537-108611

+ Details

Name:	us-gaap_ConcentrationRiskPercentage1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82913815&loc=SL49130532-203044

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82913847&loc=SL49130549-203045

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82913815&loc=SL49130531-203044

+ Details

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

- 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

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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 32
-Paragraph 2A
-URI http://asc.fasb.org/extlink&oid=82859839&loc=SL82860478-203043

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82913847&loc=SL49130543-203045

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82913847&loc=SL49130539-203045

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=82913847&loc=SL49130545-203045

+ Details

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

- Definition

Number of new stock issued during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21463-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(28))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

+ Details

Name:	us-gaap_StockIssuedDuringPeriodSharesNewIssues
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_ProductOrServiceAxis=ions_ResearchAndDevelopmentServicesForAKCEAAPOALMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ProductOrServiceAxis=ions_DeliveryOfAKCEAAPOALMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ProductOrServiceAxis=ions_ResearchAndDevelopmentServicesForAKCEAAPOCIIILMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ProductOrServiceAxis=ions_DeliveryOfAKCEAAPOCIIILMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ProductOrServiceAxis=ions_ResearchAndDevelopmentUnderCollaborativeAgreementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=ions_CollaborativeArrangementAndLicensingAgreementEnteredIntoInJanuary2017WithNovartisMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ConcentrationRiskByBenchmarkAxis=us-gaap_SalesRevenueGoodsNetMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ConcentrationRiskByTypeAxis=us-gaap_CustomerConcentrationRiskMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_ProductOrServiceAxis=ions_AKCEAAPOALMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ProductOrServiceAxis=ions_AKCEAAPOCIIILMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Collaborative Arrangements and Licensing Agreements, Novartis (Details) $ in Thousands, shares in Millions	1 Months Ended		3 Months Ended
	Jul. 31, 2017 USD ($)	Jan. 31, 2017 Drug	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($) PerformanceObligation shares	Dec. 31, 2017 USD ($)	Jul. 31, 2015 PerformanceObligation
Collaborative Arrangement and Licensing Agreement [Abstract]
Number of separate performance obligations \| PerformanceObligation						1
Revenue earned			$ 144,419	$ 115,800
Deferred revenue					$ 233,362
R&D Services for AKCEA-APO(a)-L [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Transaction price				64,000
Delivery of AKCEA-APO(a)-L [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Transaction price				1,500
R&D Services for AKCEA-APOCIII-L [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Transaction price				40,100
Delivery of AKCEA-APOCIII-L [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Transaction price				2,800
R&D Revenue Under Collaborative Agreements [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Revenue earned			102,396	$ 107,999
Novartis [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Shares issued (in shares) \| shares				1.6
Proceeds from sale of common stock				$ 100,000
Number of separate performance obligations \| PerformanceObligation				4
Transaction price				$ 108,400
Premium received on shares issued				28,400
Potential premium received if common stock is purchased in the future				5,000
Deferred revenue			$ 56,700		$ 70,700
Novartis [Member] \| Revenue [Member] \| Strategic Partner [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Concentration percentage			12.00%
Novartis [Member] \| Minimum [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Number of drugs with exclusive option that could be exercised \| Drug		1
Novartis [Member] \| R&D Revenue Under Collaborative Agreements [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Revenue earned			$ 17,100	6,100
Akcea [Member] \| AKCEA-APO(a)-L [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Maximum amount of payments receivable for milestones			600,000
Maximum amount of payments receivable for development milestones			25,000
Maximum amount of payments receivable for regulatory milestones			290,000
Maximum amount of payments receivable for commercialization milestones			$ 285,000
Royalty percentage received on sales of drug			20.00%
Akcea [Member] \| AKCEA-APOCIII-L [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Maximum amount of payments receivable for milestones			$ 530,000
Maximum amount of payments receivable for development milestones			25,000
Maximum amount of payments receivable for regulatory milestones			240,000
Maximum amount of payments receivable for commercialization milestones			$ 265,000
Royalty percentage received on sales of drug			20.00%
Akcea [Member] \| Novartis [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Upfront payment received				75,000
Portion of upfront payment retained				60,000
Portion of upfront payment paid as a sublicense fee				$ 15,000
License fee receivable per drug			$ 150,000
Percentage of license fees, milestone payments and royalties paid as sublicense fee			50.00%
Proceeds from sale of common stock to Novartis in a private placement	$ 50,000