Components of Net Periodic Pension Cost (Detail) (Pension Plans, Defined Benefit, USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Service cost, net of employee contributions	$ 26.9	$ 29.9	$ 27.8
Interest cost	21.2	18.3	19.5
Expected return on plan assets	(27.9)	(26.0)	(24.1)
Amortization of net loss	10.4	14.1	11.0
Amortization of prior service cost	(0.4)	(0.5)	(0.4)
Net periodic pension cost	$ 30.2	$ 35.8	$ 33.8