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 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 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 milestone payment to be earned under the collaboration agreement.

+ References

No definition available.

+ Details

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

- Definition

The number of programs under which drugs are to be developed and commercialized under the collaboration agreement.

+ References

No definition available.

+ Details

Name:	ions_NumberOfProgramsUnderWhichDrugsAreToBeDevelopedAndCommercialized
Namespace Prefix:	ions_
Data Type:	xbrli:integerItemType
Balance Type:	na
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_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_CollaborativeArrangementAndLicensingAgreementEnteredIntoInDecember2014WithJanssenBiotechIncMember
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:	srt_ProductOrServiceAxis=ions_IONISJBI125Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ProductOrServiceAxis=ions_IONISJBI225Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Collaborative Arrangements and Licensing Agreements, Janssen Biotech, Inc. (Details) $ in Thousands	1 Months Ended				3 Months Ended		9 Months Ended		17 Months Ended
	Jan. 31, 2018 USD ($)	Nov. 30, 2017 USD ($)	Jul. 31, 2016 USD ($)	Dec. 31, 2014 USD ($) PerformanceObligation Program	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Nov. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Collaborative Arrangement and Licensing Agreement [Abstract]
Revenue					$ 145,395	$ 118,314	$ 407,559	$ 346,387
Deferred revenue										$ 233,362
Licensing and Other Royalties [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Revenue					12,746	1,727	14,232	5,639
R&D [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Revenue					62,639	$ 83,697	225,584	$ 280,281
Janssen Biotech, Inc. [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Number of programs under which drugs are to be developed and commercialized \| Program				3
Upfront payment received				$ 35,000
Minimum amount of payments receivable for license fees and substantive milestones					800,000		800,000
Maximum amount of payments receivable for development milestones					175,000		175,000
Maximum amount of payments receivable for regulatory milestones					440,000		440,000
Maximum amount of payments receivable for commercialization milestones					180,000		180,000
Cumulative payments received					75,000		75,000
Next prospective milestone					5,000		5,000
Number of separate performance obligations \| PerformanceObligation				1
Transaction price				$ 35,000
Deferred revenue					$ 0		$ 0			$ 0
Janssen Biotech, Inc. [Member] \| Revenue [Member] \| Strategic Partner [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Concentration percentage					1.00%	3.00%	2.00%	5.00%
Janssen Biotech, Inc. [Member] \| Licensing and Other Royalties [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Revenue									$ 15,000
Janssen Biotech, Inc. [Member] \| IONIS-JBI1-2.5 [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Revenue	$ 5,000		$ 10,000
Janssen Biotech, Inc. [Member] \| IONIS-JBI2-2.5 [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Revenue		$ 5,000
Janssen Biotech, Inc. [Member] \| R&D [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Revenue					$ 900	$ 3,400	$ 6,600	$ 18,100