CONSOLIDATED STATEMENTS OF OPERATIONS (UNAUDITED) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
Revenue	$ 1,356	$ 1,240	$ 4,081	$ 3,596
Expenses
Operating	364	350	1,066	1,032
Selling, general and administrative	271	292	879	848
Restructuring	23	(1)	20	58
Depreciation and amortization	56	48	163	150
Acquisition-Related Expenses	0	0	0	3
Loss pursuant to the divestiture of MAKS	0	2	9	11
Total expenses	714	691	2,137	2,102
Operating income	642	549	1,944	1,494
Non-operating (expense) income, net
Interest expense, net	(53)	(46)	(153)	(149)
Other non-operating income, net	10	10	38	12
Total non-operating expense, net	(43)	(36)	(115)	(137)
Income before provisions for income taxes	599	513	1,829	1,357
Provision for income taxes	132	130	366	290
Net income	467	383	1,463	1,067
Less: Net (loss) income attributable to noncontrolling interests	0	3	(1)	5
Net income attributable to Moody's	$ 467	$ 380	$ 1,464	$ 1,062
Earnings per share attributable to Moody's common shareholders
Basic (in usd per share)	$ 2.49	$ 2.01	$ 7.80	$ 5.60
Diluted (in usd per share)	$ 2.47	$ 1.99	$ 7.73	$ 5.54
Weighted average number of shares outstanding
Basic (in shares)	187.8	189.0	187.6	189.6
Diluted (in shares)	189.3	191.1	189.3	191.8