Employee Benefit and Retirement Plans - Summary of Reconciliation of Change in Fair Value Measurement of Defined Benefit Plans' Consolidated Assets Using Significant Unobservable Inputs (Level 3) (Detail) - Level 3 [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	$ 6.5	$ 12.9
Realized gains (losses)	0.1
Unrealized (losses) gains		(0.4)
Purchases, sales, settlements and other, net	(4.1)	(6.0)
Fair value of plan assets at end of year	$ 2.5	$ 6.5