Basis of Presentation and Summary of Significant Accounting Policies - Allowance for Credit Losses (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable Allowance For Credit Losses [Line Items]
Balance, beginning of year	$ 14.3	$ 19.6
Credit loss expense	5.7	3.3
Write-offs and other	(4.4)	(8.6)
Balance, end of year	15.9	$ 14.3
Trade Receivables | ASC 326
Financing Receivable Allowance For Credit Losses [Line Items]
Additional allowance recognized due to adoption of Topic ASC 326	$ 0.3