Employee Benefits - Net Periodic Pension Expense (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Weighted-Average Assumptions:
Expected Long-Term Rate of Return on Assets	6.00%
Supplemental Plan
Defined Benefit plan Net periodic benefit cost
Service Cost	$ 3.7	$ 3.5	$ 3.6
Interest Cost	5.2	5.1	5.0
Settlement Expense	0.0	0.0	0.0
Amortization:
Net Loss	5.7	5.8	7.3
Prior Service Cost	0.2	0.2	0.2
Net Periodic Pension Expense	$ 14.8	$ 14.6	$ 16.1
Weighted-Average Assumptions:
Discount Rates	4.46%	4.71%	4.25%
Rate of Increase in Compensation Level	4.39%	4.25%	4.25%
U.S. Plan | Pension Plans, Defined Benefit
Defined Benefit plan Net periodic benefit cost
Service Cost	$ 38.3	$ 37.4	$ 37.8
Interest Cost	45.9	45.8	44.7
Expected Return on Plan Assets	(93.8)	(94.4)	(96.5)
Settlement Expense	0.0	0.0	0.0
Amortization:
Net Loss	19.0	18.8	29.7
Prior Service Cost	(0.4)	(0.4)	(0.4)
Net Periodic Pension Expense	$ 9.0	$ 7.2	$ 15.3
Weighted-Average Assumptions:
Discount Rates	4.46%	4.71%	4.25%
Rate of Increase in Compensation Level	4.39%	4.25%	4.25%
Expected Long-Term Rate of Return on Assets	6.75%	7.00%	7.25%
Non U.S. Plans | Pension Plans, Defined Benefit
Defined Benefit plan Net periodic benefit cost
Service Cost	$ 0.4	$ 0.0	$ 0.0
Interest Cost	4.0	4.7	5.7
Expected Return on Plan Assets	(4.5)	(4.6)	(5.9)
Settlement Expense	1.1	3.7	0.0
Amortization:
Net Loss	1.3	1.0	1.5
Prior Service Cost	0.1	0.0	0.0
Net Periodic Pension Expense	$ 2.4	$ 4.8	$ 1.3
Weighted-Average Assumptions:
Discount Rates	2.33%	3.39%	3.20%
Rate of Increase in Compensation Level	1.75%
Expected Long-Term Rate of Return on Assets	3.13%	3.73%	4.00%