Components of Net Periodic Pension Cost (Detail) (Pension Plans, Defined Benefit, USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Pension Plans, Defined Benefit
Schedule of Net Periodic Benefit Costs and Assumptions for Defined Benefit Postretirement Plans [Line Items]
Service cost, net of employee contributions	$ 27.8	$ 26.1	$ 24.6
Interest cost	19.5	19.0	18.9
Expected return on plan assets	(24.1)	(23.2)	(22.0)
Amortization of net loss	11.0	8.4	6.9
Amortization of prior service cost	(0.4)	(0.2)
Net periodic pension cost	$ 33.8	$ 30.1	$ 28.4