Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Income Tax Disclosure [Abstract]
Effective tax rate (percent)	19.90%	20.50%	14.60%	21.30%
Decrease in effective income tax due to resolution of uncertain tax positions			6.70%
Reduction resulting from lapse of applicable statute of limitations and settlement			$ 116
Excess tax benefits from stock compensation			13
Overall increase (decrease) in unrecognized tax benefits (UTPs)	$ 5		(114)
Unrecognized tax benefits, period increase (decrease), net of federal tax	$ 4		$ (115)
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 2019 through 2020 are currently under examination and 2021 through 2022 remain open to examination. The Company’s New York City tax returns for 2015 through 2019 are currently under examination. The Company’s U.K. tax returns for 2017 through 2021 remain open to examination.
Inflation reduction act impact on ETR			In August 2022, the U.S. Congress passed the Inflation Reduction Act, which included a corporate minimum tax on book earnings of 15%, an excise tax on corporate share repurchases of 1%, and certain climate change and energy tax credit incentives. The adoption of a corporate minimum tax of 15% is not expected to impact Moody’s ETR. The excise tax of 1% on corporate share buybacks will not have an impact on the Company’s ETR for 2023.