Employee Benefit Plans - Components of Net Periodic Defined Benefit Pension Benefit Cost (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 3.2	$ 2.6	$ 6.5	$ 5.2
Interest cost	5.8	6.5	11.9	12.9
Expected return on plan assets	(5.9)	(5.5)	(12.0)	(11.0)
Amortization of unrecognized: Prior service cost	0.4	0.4	0.8	0.8
Amortization of unrecognized: Net transition obligations	0.1	0.1	0.2	0.2
Actuarial losses	3.4	2.3	6.8	4.6
Total	7.0	6.4	14.2	12.7
OPEB
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.1		0.2	0.1
Interest cost	0.1	0.3	0.3	0.5
Amortization of unrecognized: Prior service cost	(0.4)	(0.4)	(0.9)	(0.9)
Total	$ (0.2)	$ (0.1)	$ (0.4)	$ (0.3)