CONSOLIDATED STATEMENT OF SHAREHOLDERS' EQUITY (DEFICIT) - USD ($) shares in Millions, $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjustment	Total Moody’s Shareholders’ Equity	Total Moody’s Shareholders’ Equity Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Capital Surplus	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Treasury Stock	Accumulated Other Comprehensive Loss	Accumulated Other Comprehensive Loss Cumulative Effect, Period of Adoption, Adjustment	Non- Controlling Interests
Beginning Balance (in shares) at Dec. 31, 2018					342.9				151.6
Beginning Balance at Dec. 31, 2018	$ 656		$ 459		$ 3	$ 601	$ 8,594		$ (8,313)	$ (426)		$ 197
Beginning Balance (Accounting Standards Update 2018-02) at Dec. 31, 2018		$ 0		$ 0				$ 20			$ (20)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,429		1,422				1,422					7
Dividends	(383)		(380)				(380)					(3)
Stock-based compensation	136		136			136
Shares issued for stock-based compensation plans at average cost, net	(32)		(32)			(70)			$ 38
Shares issued for stock-based compensation plans at average cost, net (in shares)									1.6
Purchase of noncontrolling interest	(12)		(9)			(9)						(3)
Non-controlling interest resulting from majority acquisition of Vigeo Eiris	17		0									17
Treasury shares repurchased	(991)		(991)			(16)			$ (975)
Treasury shares repurchased (in shares)									(5.2)
Currency translation adjustment, net of net investment hedge activity	33		29							29		4
Net actuarial gains (losses) and prior service cost	(24)		(24)							(24)
Amortization of prior service costs and actuarial losses	2		2							2
Ending Balance (in shares) at Dec. 31, 2019					342.9				155.2
Ending Balance at Dec. 31, 2019	$ 831		612		$ 3	642	9,656	(2)	$ (9,250)	(439)		219
Ending Balance (Accounting Standards Update 2016-13) at Dec. 31, 2019		$ (2)		$ (2)				$ (2)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	Accounting Standards Update 2016-13
Net income	$ 1,777
Net income	1,778		1,778				1,778					0
Dividends	(424)		(421)				(421)					(3)
Stock-based compensation	154		154			154
Shares issued for stock-based compensation plans at average cost, net	(53)		(53)			(58)			$ 5
Shares issued for stock-based compensation plans at average cost, net (in shares)									1.4
Purchase of noncontrolling interest	(17)		(3)			(3)						(14)
Treasury shares repurchased	(503)		(503)			0			$ (503)
Treasury shares repurchased (in shares)									(2.0)
Currency translation adjustment, net of net investment hedge activity	74		82							82		(8)
Net actuarial gains (losses) and prior service cost	(32)		(32)							(32)
Amortization of prior service costs and actuarial losses	6		6							6
Net realized and unrealized gain on cash flow hedges	(49)		(49)							(49)
Ending Balance (in shares) at Dec. 31, 2020					342.9				155.8
Ending Balance at Dec. 31, 2020	$ 1,763		1,569		$ 3	735	11,011		$ (9,748)	(432)		194
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	Accounting Standards Update 2016-13
Net income	$ 2,214		2,214				2,214					0
Dividends	(466)		(463)				(463)					(3)
Stock-based compensation	175		175			175
Shares issued for stock-based compensation plans at average cost, net	(40)		(40)			(25)			$ (15)
Shares issued for stock-based compensation plans at average cost, net (in shares)									0.7
Treasury shares repurchased	(750)		(750)			0			$ (750)
Treasury shares repurchased (in shares)									(2.2)
Currency translation adjustment, net of net investment hedge activity	(51)		(49)							(49)		(2)
Net actuarial gains (losses) and prior service cost	55		55							55
Amortization of prior service costs and actuarial losses	14		14							14
Net realized and unrealized gain on cash flow hedges	2		2							2
Ending Balance (in shares) at Dec. 31, 2021					342.9				157.3
Ending Balance at Dec. 31, 2021	$ 2,916		$ 2,727		$ 3	$ 885	$ 12,762		$ (10,513)	$ (410)		$ 189