CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Revenue	$ 4,829	$ 4,443	$ 4,204
Expenses
Operating	1,387	1,246	1,216
Selling, general and administrative	1,167	1,080	986
Restructuring	60	49	0
Depreciation and amortization	200	192	158
Acquisition-Related Expenses	3	8	23
Loss pursuant to the divestiture of MAKS	14	0	0
Total expenses	2,831	2,575	2,383
Operating income	1,998	1,868	1,821
Non-operating (expense) income, net
Interest expense, net	(208)	(215)	(209)
Other non-operating income, net	20	19	4
Purchase Price Hedge Gain	0	0	111
CCXI Gain	0	0	60
Non-operating (expense) income, net	(188)	(196)	(34)
Income before provision for income taxes	1,810	1,672	1,787
Provision for income taxes	381	352	779
Net income	1,429	1,320	1,008
Less: Net income attributable to noncontrolling interests	7	10	7
Net income attributable to Moody’s	$ 1,422	$ 1,310	$ 1,001
Earnings per share
Basic (in USD per share)	$ 7.51	$ 6.84	$ 5.24
Diluted (in USD per share)	$ 7.42	$ 6.74	$ 5.15
Weighted average shares outstanding
Basic (in shares)	189.3	191.6	191.1
Diluted (in shares)	191.6	194.4	194.2