Activity in Goodwill (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
Dec. 31, 2012	Dec. 31, 2012	Dec. 31, 2011
Goodwill [Line Items]
Goodwill beginning balance, gross		$ 642.9	$ 465.5
Goodwill beginning balance		642.9	465.5
Additions/adjustments		(4.4)	198.5
Impairment charge	(12.2)	(12.2)
Foreign currency translation adjustments		10.8	(21.1)
Goodwill ending balance, gross	649.3	649.3	642.9
Accumulated impairment charge	(12.2)	(12.2)
Goodwill ending balance	637.1	637.1	642.9
MIS
Goodwill [Line Items]
Goodwill beginning balance, gross		11.0	11.4
Goodwill beginning balance		11.0	11.4
Foreign currency translation adjustments		0.5	(0.4)
Goodwill ending balance, gross	11.5	11.5	11.0
Goodwill ending balance	11.5	11.5	11.0
MA
Goodwill [Line Items]
Goodwill beginning balance, gross		631.9	454.1
Goodwill beginning balance		631.9	454.1
Additions/adjustments		(4.4)	198.5
Impairment charge		(12.2)
Foreign currency translation adjustments		10.3	(20.7)
Goodwill ending balance, gross	637.8	637.8	631.9
Accumulated impairment charge	(12.2)	(12.2)
Goodwill ending balance	$ 625.6	$ 625.6	$ 631.9

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

+ Details