Goodwill and Other Intangibles - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
Amortization expense of intangible assets	$ 7.4	$ 5.9
Estimated amortization expense, 2013	28.4
Estimated amortization expense, 2014	28.0
Estimated amortization expense, 2015	28.0
Estimated amortization expense, 2016	27
Estimated amortization expense, 2017	27
Estimated amortization expense, 2018	$ 27