Lease Commitments - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Jan. 31, 2010
Commitments Disclosure [Line Items]
Rental expenses for operating leases	$ 22.4	$ 21.1	$ 17.2
Future minimum rental payments	58.5
Future minimum rental payments, 2013	18.0
Future minimum rental payments, 2014	16.3
Future minimum rental payments, 2015	13.8
Future minimum rental payments, 2016	7.2
Future minimum rental payments, thereafter	$ 3.2