Employee Benefits - Employee Benefit Plan Status (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplemental Plan
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	$ 129.0	$ 108.9
Projected Benefit Obligation	144.5	121.1	$ 113.9
Plan Assets at Fair Value	0.0	0.0
Funded Status at end of year	$ (144.5)	$ (121.1)
Weighted-Average Assumptions:
Discount Rates	3.79%	4.46%
Rate of Increase in Compensation Level	4.39%	4.39%
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Plan Assets at Fair Value	$ 1,506.4	$ 1,393.5
U.S. Plan | Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	1,088.4	953.2
Projected Benefit Obligation	1,209.9	1,062.7	1,006.5
Plan Assets at Fair Value	1,506.4	1,393.5	1,342.0
Funded Status at end of year	$ 296.5	$ 330.8
Weighted-Average Assumptions:
Discount Rates	3.79%	4.46%
Rate of Increase in Compensation Level	4.39%	4.39%
Expected Long-Term Rate of Return on Assets	6.00%	6.75%
Non U.S. Plans | Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	$ 192.2	$ 158.3
Projected Benefit Obligation	198.3	155.9	156.5
Plan Assets at Fair Value	178.7	139.3	$ 144.3
Funded Status at end of year	$ (19.6)	$ (16.6)
Weighted-Average Assumptions:
Discount Rates	2.08%	2.39%
Expected Long-Term Rate of Return on Assets	2.61%	3.22%