CONSOLIDATED STATEMENT OF SHAREHOLDERS' EQUITY (UNAUDITED) - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Capital Surplus	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Loss	Total Moody's Shareholders' Equity	Non- Controlling Interests
Beginning Balance (in shares) at Dec. 31, 2018		342.9			151.6
Beginning Balance at Dec. 31, 2018	$ 656	$ 3	$ 601	$ 8,594	$ (8,313)	$ (426)	$ 459	$ 197
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	374			373			373	1
Dividends	(94)			(94)			(94)
Stock-based compensation	36		36				36
Shares issued for stock-based compensation plans at average cost, net	(60)		(67)		$ 7		(60)
Shares issued for stock-based compensation plans at average cost, net (in shares)					1.0
Purchase of noncontrolling interest	(12)		(9)				(9)	(3)
Treasury shares repurchased	(448)				$ (448)		(448)
Treasury shares repurchased (in shares)					(2.7)
Cash paid for ASR contract relating to shares retained by Counterparty until final settlement	(125)		(125)				(125)
Currency translation adjustment, net of net investment hedge activity (net of tax of)	(3)					(10)	(10)	7
Net actuarial gains (losses) and prior service costs	1					1	1
Amortization of prior service costs and actuarial losses	0
Ending Balance (in shares) at Mar. 31, 2019		342.9			153.3
Ending Balance at Mar. 31, 2019	325	$ 3	436	8,893	$ (8,754)	(455)	123	202
Beginning Balance (in shares) at Dec. 31, 2019		342.9			155.2
Beginning Balance at Dec. 31, 2019	831	$ 3	642	9,656	$ (9,250)	(439)	612	219
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	487			488			488	(1)
Dividends	(101)			(101)			(101)
Stock-based compensation	37		37				37
Shares issued for stock-based compensation plans at average cost, net	(84)		(63)		$ (21)		(84)
Shares issued for stock-based compensation plans at average cost, net (in shares)					0.9
Treasury shares repurchased	(253)				$ (253)		(253)
Treasury shares repurchased (in shares)					(1.1)
Cash paid for ASR contract relating to shares retained by Counterparty until final settlement	0
Currency translation adjustment, net of net investment hedge activity (net of tax of)	(81)					(80)	(80)	(1)
Net actuarial gains (losses) and prior service costs	(1)					(1)	(1)
Amortization of prior service costs and actuarial losses	1					1	1
Net realized and unrealized gain on cash flow hedges (net of tax)	(35)					(35)	(35)
Ending Balance (in shares) at Mar. 31, 2020		342.9			155.4
Ending Balance at Mar. 31, 2020	$ 799	$ 3	$ 616	$ 10,041	$ (9,524)	$ (554)	$ 582	$ 217