Goodwill and Other Intangibles - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Goodwill and Intangible Assets Disclosure [Line Items]
Amortization expense related to other intangible assets	$ 4.6	$ 3.3
Estimated future amortization expense for 2012	15.9
Estimated future amortization expense for 2013	20.9
Estimated future amortization expense for 2014	20.8
Estimated future amortization expense for 2015	11.8
Estimated future amortization expense for 2016	$ 9.2