Components of Net Periodic Benefit Expense Related to Retirement Plans (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 21.6	$ 18.4	$ 19.8
Interest cost	16.9	16.5	13.5
Expected return on plan assets	(14.4)	(14.3)	(12.9)
Amortization of net actuarial loss from earlier periods	12.5	6.6	10.8
Amortization of net prior service costs from earlier periods	0.7	0.7	0.6
Net periodic expense	37.3	27.9	31.8
Other Retirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	2.2	1.7	1.7
Interest cost	1.0	0.9	0.8
Amortization of net actuarial loss from earlier periods	0.3		0.3
Net periodic expense	$ 3.5	$ 2.6	$ 2.8