Carrying amount as of the balance sheet date, which is the cumulative amount paid and (if applicable) the fair value of any noncontrolling interest in the acquiree, adjusted for any amortization recognized prior to the adoption of any changes in generally accepted accounting principles (as applicable) and for any impairment charges, in excess of the fair value of net assets acquired in one or more business combination transactions.

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+ Details

- Definition

Loss recognized during the period that results from the write-down of goodwill after comparing the implied fair value of reporting unit goodwill with the carrying amount of that goodwill. Goodwill is assessed at least annually for impairment.

+ References

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+ Details

- Definition

The increase (decrease) in the recorded value of goodwill for foreign currency translation adjustments and purchase accounting adjustments needed to revise the carrying amount of goodwill to fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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+ Details

Activity in Goodwill (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Goodwill [Line Items]
Beginning balance		$ 637.1
Impairment charge	(12.2)	0	(12.2)	0
Ending balance	637.1	665.2	637.1
Gross Goodwill [Member]
Goodwill [Line Items]
Beginning balance		649.3	642.9
Additions/adjustments		34.5	(4.4)
Impairment charge			0
FX translation		(6.4)	10.8
Ending balance	649.3	677.4	649.3
Accumulated Impairment Charge [Member]
Goodwill [Line Items]
Beginning balance		(12.2)	0
Additions/adjustments		0	0
Impairment charge			12.2
FX translation		0	0
Ending balance	(12.2)	(12.2)	(12.2)
Net Goodwill [Member]
Goodwill [Line Items]
Beginning balance		637.1	642.9
Additions/adjustments		34.5	(4.4)
Impairment charge			12.2
FX translation		(6.4)	10.8
Ending balance	637.1	665.2	637.1
Moodys Investors Service [Member]
Goodwill [Line Items]
Impairment charge		0	0
Moodys Investors Service [Member] \| Gross Goodwill [Member]
Goodwill [Line Items]
Beginning balance		11.5	11.0
Additions/adjustments		0	0
Impairment charge			0
FX translation		(0.1)	0.5
Ending balance	11.5	11.4	11.5
Moodys Investors Service [Member] \| Accumulated Impairment Charge [Member]
Goodwill [Line Items]
Beginning balance		0	0
Additions/adjustments		0	0
Impairment charge			0
FX translation		0	0
Ending balance	0	0	0
Moodys Investors Service [Member] \| Net Goodwill [Member]
Goodwill [Line Items]
Beginning balance		11.5	11.0
Additions/adjustments		0	0
Impairment charge			0
FX translation		(0.1)	0.5
Ending balance	11.5	11.4	11.5
Moodys Analytics [Member]
Goodwill [Line Items]
Impairment charge		0	(12.2)
Moodys Analytics [Member] \| Gross Goodwill [Member]
Goodwill [Line Items]
Beginning balance		637.8	631.9
Additions/adjustments		34.5	(4.4)
Impairment charge			0
FX translation		(6.3)	10.3
Ending balance	637.8	666.0	637.8
Moodys Analytics [Member] \| Accumulated Impairment Charge [Member]
Goodwill [Line Items]
Beginning balance		(12.2)
Additions/adjustments		0
Impairment charge			12.2
FX translation		0
Ending balance	(12.2)	(12.2)	(12.2)
Moodys Analytics [Member] \| Net Goodwill [Member]
Goodwill [Line Items]
Beginning balance		625.6	631.9
Additions/adjustments		34.5	(4.4)
Impairment charge			12.2
FX translation		(6.3)	10.3
Ending balance	$ 625.6	$ 653.8	$ 625.6