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Organization and Significant Accounting Policies, Cash, Cash Equivalents and Investments (Details)	Dec. 31, 2019 Company
Cash, Cash Equivalents and Investments [Abstract]
Number of publicly-held companies in which there is an equity ownership interest of less than 20%	2
Number of privately-held companies in which there is an equity ownership interest of less than 20%	5

X

- Definition

Number of privately-held companies, in which the entity has an equity ownership interest of less than 20%, with which it conducts business. These are accounted for under the cost method.

+ References

No definition available.

+ Details

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X

- Definition

Number of publicly-held companies, in which the entity has an equity ownership interest of less than 20%, with which it conducts business. These are accounted for at fair value.

+ References

No definition available.

+ Details

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

X

- References

No definition available.

+ Details

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