Goodwill and Other Intangibles - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Goodwill and Intangible Assets Disclosure [Line Items]
Amortization expense of intangible assets	$ 26.8	$ 25.2	$ 23.7
Estimated amortization expense, 2013	29
Estimated amortization expense, 2014	28
Estimated amortization expense, 2015	28
Estimated amortization expense, 2016	28
Estimated amortization expense, 2017	28
Estimated amortization expense, 2018	$ 28