Unaudited Pro Forma Information (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010
Business Acquisition [Line Items]
Revenue	$ 4,360.4		$ 4,134.6
Net income (loss)	$ (18.9)		$ 158.1
Net income (loss) per share - basic	$ (0.42)		$ 3.47
Net income (loss) per share - diluted	$ (0.42)	[1]	$ 3.41	[1]
Weighted average shares outstanding - basic	45.2		45.6
Weighted average shares outstanding - diluted	45.2	[1]	46.3	[1]

[1] Weighted average shares outstanding and per diluted share amounts in 2011 exclude common stock equivalents, since the impact of these instruments would be antidilutive.