CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Net income	$ 324.4	$ 228.4	$ 546.1	$ 419.5
Foreign currency translation adjustment-Pre Tax Amount	14.1	(13.0)	9.3	(72.8)
Foreign currency translation adjustment-Tax Amount	0	0	0	0
Foreign currency translation adjustments-Net of Tax	14.1	(13.0)	9.3	(72.8)
Cash Flow And Net Investment Hedges [Abstract]
Net unrealized gain (losses) on cash flow and net investment hedges- Pre Tax	(2.7)	(0.4)	(6.3)	1.0
Net unrealized gain (losses) on cash flow and net investment hedges-Tax Amount	(1.1)	(0.1)	(2.6)	0.5
Net unrealized losses on cash flow and net investment hedges	(1.6)	(0.3)	(3.7)	0.5
Reclassification of losses included in net income-Pre Tax	0	0.1	0	0.7
Reclassification of losses included in net income-Tax Amount	0	0	0	0.2
Reclassification of losses included in net income- Net of Tax	0	0.1	0	0.5
Pension and Other Retirement Benefits Net of Tax [Abstract]
Amortization of actuarial losses and prior service costs included in net income (pre-tax)	(2.0)	(2.8)	(3.7)	(5.9)
Amortization of actuarial losses and prior service costs included in net income	(1.2)	(1.6)	(1.4)	(3.5)
Net actuarial losses and prior service costs (pre-tax)	(6.9)	0.9	(6.9)	0.9
Net actuarial losses and prior service costs (tax)	2.8	(0.4)	2.8	(0.4)
Net actuarial losses and prior service costs	(4.1)	0.5	(4.1)	0.5
Total other comprehensive income (loss)-Pre Tax	10.9	(9.6)	4.2	(64.3)
Net current period other comprehensive income/(loss)	(3.1)	1.5	(3.1)	3.5
Total other comprehensive income (loss)-Net of Tax	14.0	(11.1)	7.3	(67.8)
Comprehensive income (loss)	338.4	217.3	553.4	351.7
Comprehensive income attributable to noncontrolling interests and redeemable noncontrolling interest	5.2	2.9	8.9	5.6
Comprehensive income attributable to Moody's	333.2	214.4	544.5	346.1
Foreign Currency Translation Adjustment Reclassification Of Losses To Net Income Pursuant To Icra Step Acquisition Pre Tax	4.4	0	4.4	0
Foreign Currency Translation Adjustment Reclassification Of Losses To Net Income Pursuant To Icra Step Acquisition Tax	0	0	0	0
Foreign Currency Translation Adjustment Reclassification Of Losses To Net Income Pursuant To Icra Step Acquisition Net Of Tax	$ 4.4	$ 0	$ 4.4	$ 0