Allowance for Doubtful Accounts (Tables)

9 Months Ended

Sep. 30, 2021

Receivables [Abstract]

Summary of Allowance for Doubtful Accounts

The allowance for doubtful accounts consisted of the following (in millions):

	September 30,
	2021			2020
Balance at beginning of year	$	3.0		$	3.1
Provision charged to expense		(0.9	)		0.2
Write-offs, less recoveries		—			(0.3	)
Balance at end of period	$	2.1		$	3.0