Allowance for Doubtful Accounts - Summary of Allowance for Doubtful Accounts (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Debt Disclosure [Abstract]
Balance at beginning of year	$ 3.1	$ 2.1
Provision charged to expense	0.1
Write-offs, less recoveries		(0.1)
Balance at end of period	$ 3.2	$ 2.0