Employee Benefit Plans - Additional Information (Detail) - Defined Benefit Pension Plans - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Defined Benefit Plan Disclosure [Line Items]
Estimated Decrease in Pension Expense for 2017 due to change of method used to estimate service cost and interest cost components of pension expense from a single weighted-average method to an individual spot rate approach	$ 15.0		$ 15.0
Contribution to pension plans	$ 4.9	$ 5.8	$ 15.3	$ 65.1