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Significant Accounting Policies, Noncontrolling Interest in Akcea (Details) | Sep. 30, 2020 | Jun. 30, 2017
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Akcea [Member] |  |
Noncontrolling Interest in Akcea Therapeutics, Inc. [Abstract] |  |
Percentage ownership | 76.00% | 100.00%

X
- Definition The parent entity's interest in net assets of the subsidiary, expressed as a percentage. + References No definition available. + Details
Name: | us-gaap_MinorityInterestOwnershipPercentageByParent
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | srt_OwnershipAxis=ions_AkceaTherapeuticsIncMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |