CONSOLIDATED STATEMENT OF SHAREHOLDERS' EQUITY (DEFICIT) - 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, 2016		342.9			152.2
Beginning Balance at Dec. 31, 2016	$ (1,027)	$ 3	$ 477	$ 6,689	$ (8,030)	$ (364)	$ (1,225)	$ 198
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,008			1,001			1,001	7
Dividends	(223)			(220)			(220)	(3)
Stock-based compensation	123		123				123
Shares issued for stock-based compensation plans at average cost, net (in shares)					1.9
Shares issued for stock-based compensation plans at average cost, net	10		(67)		$ 77		10
Purchase of noncontrolling interest	(5)		(4)				(4)	(1)
Treasury shares repurchased (in shares)					(1.6)
Treasury shares repurchased	(200)				$ (200)		(200)
Currency translation adjustment, net of net investment hedge activity	189					176	176	13
Net actuarial gains (losses) and prior service costs	13					13	13
Amortization of prior service costs and actuarial losses	5					5	5
Net unrealized gain on available for sale securities	(2)					(1)	(1)	(1)
Net realized and unrealized gain on cash flow hedges (net of tax of $1 million)	(1)					(1)	(1)
Ending Balance (in shares) at Dec. 31, 2017		342.9			151.9
Ending Balance at Dec. 31, 2017	(115)	$ 3	529	7,465	$ (8,153)	(172)	(328)	213
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,320			1,310			1,310	10
Dividends	(343)			(339)			(339)	(4)
Stock-based compensation	131		131				131
Shares issued for stock-based compensation plans at average cost, net (in shares)					1.5
Shares issued for stock-based compensation plans at average cost, net	(16)		(59)		$ 43		(16)
Treasury shares repurchased (in shares)					(1.2)
Treasury shares repurchased	(203)				$ (203)		(203)
Currency translation adjustment, net of net investment hedge activity	(281)					(259)	(259)	(22)
Net actuarial gains (losses) and prior service costs	4					4	4
Amortization of prior service costs and actuarial losses	4					4	4
Net realized and unrealized gain on cash flow hedges (net of tax of $1 million)	(1)					(1)	(1)
Ending Balance (in shares) at Dec. 31, 2018		342.9			151.6
Ending Balance at Dec. 31, 2018	656	$ 3	601	8,594	$ (8,313)	(426)	459	197
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 (in shares)					1.6
Shares issued for stock-based compensation plans at average cost, net	(32)		(70)		$ 38		(32)
Purchase of noncontrolling interest	(12)		(9)				(9)	(3)
Non-controlling interest resulting from majority acquisition of Vigeo Eiris	17							17
Treasury shares repurchased (in shares)					(5.2)
Treasury shares repurchased	(991)		(16)		$ (975)		(991)
Currency translation adjustment, net of net investment hedge activity	33					29	29	4
Net actuarial gains (losses) and prior service costs	(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	$ 3	$ 642	$ 9,656	$ (9,250)	$ (439)	$ 612	$ 219