No definition available.

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

- Definition

Cumulative amount of payments received under the collaboration agreement as of the end of the reporting period.

+ References

No definition available.

+ Details

Name:	ions_CumulativePaymentsReceived
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 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 minimum amount of payments receivable for license fees and substantive milestones under the collaboration agreement.

+ References

No definition available.

+ Details

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

- Definition

The next potential payment to be earned under the collaboration agreement.

+ References

No definition available.

+ Details

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

- Definition

The number of drugs that can be licensed by the partner(s) under their respective collaboration agreements.

+ References

No definition available.

+ Details

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

- Definition

The number of obligations fully satisfied under the collaboration agreement for which revenue is recognized over the period of performance.

+ References

No definition available.

+ Details

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

- Definition

The number of programs advanced under the collaboration agreement.

+ References

No definition available.

+ Details

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

- Definition

Total payments received since inception of the collaboration agreement included in the transaction price for the performance obligation.

+ References

No definition available.

+ Details

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

- 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 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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6351-108592

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=109250915&loc=d3e13531-108611

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109250915&loc=d3e13537-108611

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6404-108592

+ 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://fasb.org/us-gaap/role/ref/legacyRef
-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

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-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 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130549-203045

+ Details

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

- 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_ProductOrServiceAxis=ions_ResearchAndDevelopmentRevenueUnderCollaborativeAgreementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	srt_ProductOrServiceAxis=ions_IONISAZ525Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ProductOrServiceAxis=ions_IONISAZ625Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=ions_CollaborativeArrangementAndLicensingAgreementEnteredIntoInDecember2012WithAstraZenecaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

Collaborative Arrangements and Licensing Agreements, AstraZeneca (Details) $ in Thousands	1 Months Ended			3 Months Ended			12 Months Ended
	Jul. 31, 2015 USD ($) PerformanceObligation	May 31, 2015 USD ($)	Dec. 31, 2012 USD ($) PerformanceObligation	Dec. 31, 2018 USD ($) Drug Program	Sep. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($) Drug	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Mar. 31, 2014 PerformanceObligation
Collaborative Arrangement and Licensing Agreement [Abstract]
Revenue		$ 91,200					$ 599,674	$ 514,179	$ 372,776
Deferred revenue								233,362
R&D [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Revenue							344,752	394,165	$ 350,009
AstraZeneca [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Deferred revenue				$ 40,100			$ 40,100	$ 57,700
AstraZeneca [Member] \| Revenue [Member] \| Strategic Partner [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Concentration percentage							20.00%	4.00%	11.00%
AstraZeneca [Member] \| R&D [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Revenue							$ 120,700	$ 21,600	$ 41,300
Cardiac, Renal and Metabolic Diseases [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Number of drugs that can be licensed under option in collaboration agreements \| Drug				3			3
Upfront payment received	$ 65,000
Minimum amount of payments receivable for license fees and substantive milestones				$ 4,000,000			$ 4,000,000
Maximum amount of payments receivable for development milestones				1,100,000			1,100,000
Maximum amount of payments receivable for regulatory milestones				2,900,000			2,900,000
Cumulative payments received				165,000			165,000
Next prospective payment				10,000			10,000
Number of separate performance obligations \| PerformanceObligation	1
Transaction price	$ 65,000
Revenue					$ 10,000
Cardiac, Renal and Metabolic Diseases [Member] \| IONIS-AZ5-2.5 [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Revenue						$ 30,000
Cardiac, Renal and Metabolic Diseases [Member] \| IONIS-AZ6-2.5 [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Revenue						$ 30,000
Cardiac, Renal and Metabolic Diseases [Member] \| R&D [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Payments included in transaction price for performance obligation				90,000			90,000
Revenue					$ 10,000
Oncology [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Upfront payment received			$ 31,000
Minimum amount of payments receivable for license fees and substantive milestones				450,000			450,000
Maximum amount of payments receivable for development milestones				152,000			152,000
Maximum amount of payments receivable for regulatory milestones				275,000			275,000
Cumulative payments received				125,000			125,000
Next prospective payment				$ 25,000			$ 25,000
Number of programs advanced \| Program				2
Number of separate performance obligations \| PerformanceObligation			4
Transaction price			$ 31,000
Number of obligations fully satisfied \| PerformanceObligation										3
Revenue				$ 30,000
Oncology [Member] \| Danvatirsen [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Revenue				17,500
Oncology [Member] \| Undisclosed Program [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Revenue				$ 10,000
Oncology [Member] \| R&D [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Transaction price			$ 7,600