Components of Net Periodic Pension Cost (Detail) (Pension Plans, Defined Benefit, USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Service cost, net of employee contributions	$ 7.5	$ 6.7
Interest cost	5.0	5.3
Expected return on plan assets	(7.8)	(6.8)
Amortization	2.9	2.4
Net periodic pension cost	$ 7.6	$ 7.6