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Pension and Other Retirement Benefits - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2026	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Defined Benefit Plans and Other Postretirement Benefit Plans [Abstract]
Moody's shares held in ESOP		282,442	304,076
Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans [Abstract]
Employer contributions		$ 6	$ 11
Other Retirement Plans
Defined Benefit Plans and Other Postretirement Benefit Plans [Abstract]
Employer contributions		$ 1	1
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		$ 67	$ 73	$ 71
U.S. Plans \| Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans [Abstract]
Expected rate of return		6.60%	6.10%	6.55%
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%
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		$ 61	$ 50	$ 42
Forecast \| U.S. Plans \| Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans [Abstract]
Expected rate of return	6.95%