Goodwill and Other Intangibles - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Goodwill and Intangible Assets Disclosure [Line Items]
Estimated future amortization expense for 2012	$ 5.4		$ 5.4
Estimated future amortization expense for 2013	20.8		20.8
Estimated future amortization expense for 2014	20.7		20.7
Estimated future amortization expense for 2015	11.7		11.7
Estimated future amortization expense for 2016	9.1		9.1
Other Intangible Assets
Goodwill and Intangible Assets Disclosure [Line Items]
Amortization expense related to other intangible assets	$ 5.2	$ 5.3	$ 15.0	$ 11.5