Background and Basis of Presentation - Allowance for Uncollectible Accounts Receivable (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accounts receivable, allowances	$ 1.7		$ 1.7		$ 1.5
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for (reversal of) uncollectible accounts receivable	$ (0.3)		$ 0.7	$ 0.0
COVID-19
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for (reversal of) uncollectible accounts receivable		$ 1.0