Consolidated Statements of Operations (USD $) In Millions, except Per Share data	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Consolidated Statements of Operations [Abstract]
Revenue	$ 531.3	$ 513.3	$ 1,713.6	$ 1,467.7
Expenses
Operating	171.0	153.7	502.3	423.9
Selling, general and administrative	145.0	152.2	436.4	418.5
Restructuring	0.2	0.4	0.1
Depreciation and amortization	19.0	18.1	58.5	49.1
Total expenses	335.2	324.4	997.3	891.5
Operating Income	196.1	188.9	716.3	576.2
Non-operating (expense) income, net
Interest expense, net	(12.9)	(12.8)	(45.2)	(35.1)
Other non-operating income, net	1.6	5.3	13.1	0.7
Total non-operating (expense) income, net	(11.3)	(7.5)	(32.1)	(34.4)
Income before provisions for income taxes	184.8	181.4	684.2	541.8
Provision for income taxes	52.7	44.2	204.3	167.3
Net income	132.1	137.2	479.9	374.5
Less: Net income attributable to noncontrolling interests	1.4	1.2	4.7	4.1
Net income attributable to Moody's	$ 130.7	$ 136.0	$ 475.2	$ 370.4
Earnings per share attributable to Moody's common shareholders
Basic	$ 0.58	$ 0.58	$ 2.09	$ 1.57
Diluted	$ 0.57	$ 0.58	$ 2.06	$ 1.56
Weighted average number of shares outstanding
Basic	226.0	234.3	227.7	235.5
Diluted	229.0	235.7	230.7	237.1
Dividends declared per share attributable to Moody's common shareholders	$ 0.14	$ 0.105	$ 0.28	$ 0.21