Other Post-Employment Benefits and Other Employee Benefit Plans - Components of Net Periodic Benefit Cost (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Components of net periodic benefit cost:
Service cost	$ 4.3	$ 7.0	$ 10.6
Interest cost	21.7	22.9	26.1
Amortization of net loss	3.3	6.5	7.5
Amortization of prior service credit	0.0	(0.1)	0.0
Income of settlement/curtailment	4.4	5.1	0.7
Total benefit (income) cost	(4.1)	1.0	11.9
Other Post-Employment Benefits and Other Employee Benefit Plans
Components of net periodic benefit cost:
Service cost	0.1	0.1	0.2
Interest cost	1.4	1.6	1.9
Amortization of net loss	(0.2)	(0.2)	0.0
Amortization of prior service credit	(0.3)	(1.2)	(1.6)
Net periodic benefit cost	1.0	0.3	0.5
Income of settlement/curtailment	0.0	(13.5)	0.0
Total benefit (income) cost	$ 1.0	$ (13.2)	$ 0.5