Other Post-Employment Benefits and Other Employee Benefit Plans - Accumulated Other Comprehensive Loss Expected to be Recognized as Components of Net Periodic Benefit Cost (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Unrecognized prior service costs	$ 0.0
Unrecognized net actuarial loss	(3.5)
Total	(3.5)
Other Post-Employment Benefits and Other Employee Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Unrecognized prior service costs	(0.3)
Unrecognized net actuarial loss	(0.2)
Total	$ (0.5)