Reconciliation of Gross Amount of Unrecognized Tax Benefits (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Schedule of Unrecognized Tax Benefits [Line Items]
Balance, January 1	$ 45.0	$ 53.6
Additions related to prior year tax positions	1.7	4.5
Reductions related to prior year tax positions	(5.3)	(9.0)
Additions for tax positions of the current year	7.2	8.1
Settlements	(2.8)	(11.3)
Lapse of statutes of limitation	(2.4)	(0.9)
Balance, December 31	$ 43.4	$ 45.0