CONSOLIDATED STATEMENTS OF OPERATIONS (UNAUDITED) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Statement [Abstract]
Revenue	$ 1,553	$ 1,435	$ 3,153	$ 2,725
Expenses
Operating	365	362	758	702
Selling, general and administrative	327	307	620	608
Depreciation and amortization	60	58	119	107
Restructuring	0	(2)	2	(3)
Loss pursuant to the divestiture of MAKS	0	0	0	9
Total expenses	752	725	1,499	1,423
Operating income	801	710	1,654	1,302
Non-operating (expense) income, net
Interest expense, net	(49)	(60)	(56)	(100)
Other non-operating income, net	6	16	22	28
Total non-operating (expense) income, net	(43)	(44)	(34)	(72)
Income before provision for income taxes	758	666	1,620	1,230
Provision for income taxes	181	157	307	234
Net income	577	509	1,313	996
Less: Net income (loss) attributable to noncontrolling interests	0	0	0	(1)
Net income attributable to Moody's	$ 577	$ 509	$ 1,313	$ 997
Earnings per share attributable to Moody's common shareholders
Basic (in usd per share)	$ 3.09	$ 2.71	$ 7.02	$ 5.31
Diluted (in usd per share)	$ 3.07	$ 2.69	$ 6.98	$ 5.27
Weighted average number of shares outstanding
Basic (in shares)	186.7	187.7	187.0	187.6
Diluted (in shares)	187.9	189.0	188.2	189.3