Estimated Fair Value of Net Assets Acquired and Liabilities Assumed at Acquisition Dates (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
Schedule of Business Acquisitions, Purchase Price Allocation [Line Items]
Current assets	$ 14.1		$ 6.0
Property and equipment	4.2		0.3
Other assets	0.1		0.6
Identifiable intangible assets	52.2	[1]	30.6	[1]
Goodwill	75.6	[2]	47.5	[2]
Total assets acquired	146.2		85.0
Total liabilities assumed	(13.8)		(8.0)
Non-controlling interest			(0.4)
Net assets acquired	$ 132.4		$ 76.6

[1] Identifiable intangible assets are further disaggregated in the following table.

[2] Of the goodwill resulting from 2011 and 2010 acquisitions, $44.7 million and $4.4 million, respectively, is tax deductible.