Components of Net Periodic Pension Cost (Detail) (Pension Plans, Defined Benefit, USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Pension Plans, Defined Benefit
Pension and Other Postretirement Benefits Disclosure [Line Items]
Service cost, net of employee contributions	$ 7.0	$ 6.8	$ 20.8	$ 20.3
Interest cost	4.9	4.8	14.6	14.2
Expected return on plan assets	(6.2)	(5.9)	(17.9)	(17.6)
Amortization	2.8	1.9	7.8	5.9
Net periodic pension cost	$ 8.5	$ 7.6	$ 25.3	$ 22.8