Revenue from Contracts with Customers - Provision for Doubtful Accounts (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Change in the allowance for doubtful accounts
Balance at beginning of period	$ 7.8	$ 8.2	$ 7.5	$ 7.5
Provision charged to expense	3.4	5.2	12.5	12.5
Accounts written off, net of recoveries	(3.1)	(4.7)	(11.9)	(11.3)
Balance at end of period	8.1	$ 8.7	8.1	$ 8.7
Allowance for doubtful accounts for non-trade accounts receivable	$ 1.8		$ 1.8