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Pension and Other Retirement Benefits - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plans and Other Postretirement Benefit Plans [Abstract]
Dividends paid on ESOP		$ 1,000,000	$ 1,000,000	$ 1,000,000
Moody's shares held in ESOP		315,400	329,300
U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans [Abstract]
Employee contribution percentage of employee contribution in participation		50.00%
Maximum employee contribution in profit participation plan		3.00%
Defined contribution compensation expense		$ 71,000,000	$ 35,000,000	$ 54,000,000
U.S. Plans \| Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans [Abstract]
Expected rate of return		6.55%	5.05%	5.45%
Employer contributions		$ 11,000,000	$ 7,000,000
U.S. Plans \| Other Retirement Plans
Defined Benefit Plans and Other Postretirement Benefit Plans [Abstract]
Expected rate of return		0.00%	0.00%	0.00%
Employer contributions		$ 1,000,000	$ 1,000,000
U.S. Plans \| Equity Securities \| Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans [Abstract]
Plan asset, target asset allocation percentage		35.00%
U.S. Plans \| Equity Securities \| Pension Plans \| Minimum
Defined Benefit Plans and Other Postretirement Benefit Plans [Abstract]
Plan asset, target asset allocation percentage		23.00%
U.S. Plans \| Equity Securities \| Pension Plans \| Maximum
Defined Benefit Plans and Other Postretirement Benefit Plans [Abstract]
Plan asset, target asset allocation percentage		46.00%
U.S. Plans \| Fixed Income Securities \| Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans [Abstract]
Plan asset, target asset allocation percentage		61.00%
U.S. Plans \| Fixed Income Securities \| Pension Plans \| Minimum
Defined Benefit Plans and Other Postretirement Benefit Plans [Abstract]
Plan asset, target asset allocation percentage		44.00%
U.S. Plans \| Fixed Income Securities \| Pension Plans \| Maximum
Defined Benefit Plans and Other Postretirement Benefit Plans [Abstract]
Plan asset, target asset allocation percentage		77.00%
U.S. Plans \| Other Investments \| Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans [Abstract]
Plan asset, target asset allocation percentage		5.00%
U.S. Plans \| Other Investments \| Pension Plans \| Minimum
Defined Benefit Plans and Other Postretirement Benefit Plans [Abstract]
Plan asset, target asset allocation percentage		2.00%
U.S. Plans \| Other Investments \| Pension Plans \| Maximum
Defined Benefit Plans and Other Postretirement Benefit Plans [Abstract]
Plan asset, target asset allocation percentage		8.00%
Non-U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans [Abstract]
Defined contribution compensation expense		$ 42,000,000	37,000,000	$ 32,000,000
Unfunded Plan \| U.S. Plans \| Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans [Abstract]
Employer contributions		$ 11,000,000	$ 7,000,000
Forecast \| U.S. Plans \| Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans [Abstract]
Expected rate of return	6.10%
Forecast \| Funded Plan \| Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans [Abstract]
Employer contributions	$ 0
Forecast \| Unfunded Plan \| U.S. Plans \| Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans [Abstract]
Employer contributions	$ 13,000,000