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Significant Accounting Policies, Amendments to Equity Plan (Details) - shares | Jun. 30, 2021 | Mar. 31, 2021
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2020 Equity Incentive Plan [Member] |  |
Amendments to Equity Plans [Abstract] |  |
Number of shares authorized for issuance under the Plan (in shares) | 1,600,000 | 2,600,000
2011 Equity Incentive Plan [Member] |  |
Amendments to Equity Plans [Abstract] |  |
Number of shares authorized for issuance under the Plan (in shares) | 29,700,000 | 23,000,000.0
Reduction in fungible share reserve for each share issued pursuant to full value award (n shares) | (1.7) |
Increase in fungible share reserve for each share returning from a full value award (in shares) | 1.7 |

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- Definition Increase (decrease) in the number of shares in the "fungible" share reserve for each share issued pursuant to full value award. + References No definition available. + Details
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Namespace Prefix: | ions_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

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- Definition Increase (decrease) in the number of shares in the "fungible" share reserve for each share of common stock returning from a full value award. + References No definition available. + Details
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- References No definition available. + Details
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- Definition Number of shares authorized for issuance under share-based payment arrangement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Details
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- Details
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