CONSOLIDATED STATEMENTS OF OPERATIONS (UNAUDITED) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Revenue	$ 1,240.5	$ 1,080.8	$ 3,596.2	$ 3,382.6
Expenses
Operating	350.2	306.3	1,031.8	941.4
Selling, general and administrative	291.9	260.3	848.1	801.9
Restructuring	(1.0)	0.0	58.3	0.0
Depreciation and amortization	48.6	46.1	149.9	143.6
Acquisition-Related Expenses	0.0	1.3	3.4	4.1
Impairment pursuant to the planned divestiture of MAKS	2.0	0.0	10.7	0.0
Total expenses	691.7	614.0	2,102.2	1,891.0
Operating income	548.8	466.8	1,494.0	1,491.6
Non-operating (expense) income, net
Interest expense, net	(45.9)	(56.4)	(149.0)	(160.5)
Other non-operating income, net	9.9	2.4	12.6	18.3
Total non-operating expense, net	(36.0)	(54.0)	(136.4)	(142.2)
Income before provisions for income taxes	512.8	412.8	1,357.6	1,349.4
Provision for income taxes	130.4	100.8	289.6	282.7
Net income	382.4	312.0	1,068.0	1,066.7
Less: Net income attributable to noncontrolling interests	3.0	1.8	5.4	7.4
Net income attributable to Moody's	$ 379.4	$ 310.2	$ 1,062.6	$ 1,059.3
Earnings per share attributable to Moody's common shareholders
Basic (in usd per share)	$ 2.01	$ 1.62	$ 5.60	$ 5.53
Diluted (in usd per share)	$ 1.99	$ 1.59	$ 5.54	$ 5.45
Weighted average number of shares outstanding
Basic (in shares)	189.0	191.8	189.6	191.7
Diluted (in shares)	191.1	194.5	191.8	194.4