Other Post-Employment Benefits and Other Employee Benefit Plans - Estimated Future Benefit Payments (Detail) $ in Millions	Dec. 31, 2017 USD ($)
Defined Benefit Plan Disclosure [Line Items]
2018	$ 43.2
2019	38.4
2020	38.8
2021	42.2
2022	44.2
Thereafter	220.5
Total	427.3
Other Post-Employment Benefits and Other Employee Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
2018	5.3
2019	5.3
2020	5.1
2021	4.9
2022	4.4
Thereafter	16.5
Total	$ 41.5