Changes in Carrying Amount of Goodwill (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Mar. 31, 2013
Goodwill [Roll Forward]
Beginning Balance		$ 96.7	$ 73.7	$ 96.9
Acquisitions and adjustments to purchase price		0.2	24.7
Impairment charge	(1.5)		(1.5)
Changes due to foreign currency translation		0.1	(0.2)
Ending Balance	$ 96.7	$ 97.0	$ 96.7	$ 96.9

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

The aggregate amount of goodwill acquired in the period and allocated to the reportable segment. The value is stated at fair value based on the purchase price allocation.

+ References+ 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