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Income Taxes - Additional Information (Detail) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Dec. 31, 2025 | Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024
Income Tax Examination [Line Items] |  |  |  |  |
Effective tax rate (percent) |  | 25.40% | 24.00% | 24.20% | 23.50%
Excess tax benefits from stock compensation |  |  |  | $ 30 |
Unrecognized tax benefits, period increase (decrease), net of federal tax benefits |  | $ 5 |  | 19 |
Unrecognized tax benefits, period increase (decrease) |  |  |  | $ 21 |
Income tax examination, description |  |  |  | Moody’s is subject to U.S. federal income tax as well as income tax in various state, local and foreign jurisdictions. The Company's U.S. federal income tax returns for 2021 through 2024 remain open to examination. The Company’s New York City tax returns for 2018 through 2022 are currently under examination, and 2023 is open to examination. The Company's U.K. corporate income tax returns are currently under audit for years 2017 through 2021, while years 2022 through 2023 remain open to examination. |
Forecast |  |  |  |  |
Income Tax Examination [Line Items] |  |  |  |  |
Unrecognized tax benefits, reduction resulting from lapse of applicable statute of limitations | $ 64 |  |  |  |
Unrecognized tax benefits, reduction resulting from lapse of applicable statute of limitations, related interest | $ 15 |  |  |  |

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- Definition Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations, Related Interest + References No definition available. + Details
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- Definition Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 12 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482685/740-10-50-12 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 231 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482663/740-10-55-231 + Details
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- Definition Amount of difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying domestic federal statutory income tax rate to pretax income (loss) from continuing operation, attributable to expense for award under share-based payment arrangement. Excludes expense determined to be nondeductible upon grant or after for award under share-based payment arrangement. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 718 -SubTopic 740 -Name Accounting Standards Codification -Section 35 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479176/718-740-35-2 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 12 -Subparagraph (b)(3) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482685/740-10-50-12 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 12 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482685/740-10-50-12 + Details
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- Definition A brief description of status of the tax examination, significant findings to date, and the entity's position with respect to the findings. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 15 -Subparagraph (e) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482685/740-10-50-15 + Details
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- Definition Amount of increase (decrease) in unrecognized tax benefits attributable to uncertain tax positions taken in tax returns. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 15A -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482685/740-10-50-15A + Details
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- Definition Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 15A -Subparagraph (a)(4) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482685/740-10-50-15A + Details
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