Basis of Presentation and Summary of Significant Accounting Policies - Transactions Affecting Allowance for Doubtful Accounts (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Receivables [Abstract]
Balance, beginning of year	$ 25.9	$ 32.4	$ 35.9
Provision for doubtful accounts receivable	7.4	13.3	3.2
Write-offs and other	(12.8)	(19.8)	(6.7)
Balance, end of year	$ 20.5	$ 25.9	$ 32.4