CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Net income	$ 815.9	$ 699.7	$ 578.0
Foreign currency translation adjustment-Pre Tax Amount	(15.8)	35.4	(50.3)
Foreign currency translation adjustment-Tax Amount	0.6	(0.2)	1.6
Foreign currency translation adjustments-Net of Tax	(15.2)	35.2	(48.7)
Cash Flow And Net Investment Hedges [Abstract]
Net unrealized gain (losses) on cash flow and net investment hedges- Pre Tax	6.3	(3.9)	(1.0)
Net unrealized gain (losses) on cash flow and net investment hedges-Tax Amount	2.6	(1.6)	(0.4)
Net unrealized losses on cash flow and net investment hedges	3.7	(2.3)	(0.6)
Reclassification of losses included in net income-Pre Tax	1.2	4.1	5.3
Reclassification of losses included in net income-Tax Amount	0.5	1.7	2.1
Reclassification of losses included in net income - Net of Tax	0.7	2.4	3.2
Pension and Other Retirement Benefits Net of Tax [Abstract]
Amortization Of Actuarial Losses And Prior Service Costs Included In Net Income Pre Tax	11.9	10.0	7.4
Amortization Of Actuarial Losses And Prior Service Costs Included In Net Income Tax	4.9	4.1	3.0
Amortization Of Actuarial Losses And Prior Service Costs Included In Net Income Net Of Tax	7.0	5.9	4.4
Net Actuarial Losses And Prior Service Costs Pre Tax	50.9	(26.0)	(56.3)
Net Actuarial Losses And Prior Service Costs Tax Effect	21.0	(11.2)	(22.1)
Net Actuarial Losses And Prior Service Costs Net Of Tax	29.9	(14.8)	(34.2)
Total other comprehensive income (loss)-Pre Tax	55.9	19.6	(94.9)
Net current period other comprehensive income/(loss)	28.4	(6.8)	(19.0)
Total other comprehensive income (loss)-Net of Tax	27.5	26.4	(75.9)
Comprehensive income (loss)	843.4	726.1	502.1
Comprehensive income attributable to noncontrolling interests and redeemable noncontrolling interest	11.4	10.7	4.8
Comprehensive income attributable to Moody's	832.0	715.4	497.3
Foreign currency translation adjustments - reclassification of losses included in net income due to liquidation of a foreign subsidiary Pre Tax	1.4	0	0
Foreign currency translation adjustments - reclassification of losses included in net income due to liquidation of a foreign subsidiary Tax Effect	0	0	0
Foreign currency translation adjustments - reclassification of losses included in net income due to liquidation of a foreign subsidiary Net of Tax	$ 1.4	$ 0	$ 0