Summary of Significant Accounting Policies - Receivables (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Allowance for doubtful accounts receivable	$ 9.5	$ 4.6	$ 7.3	$ 6.6
Provision for doubtful accounts	14.3	6.5	11.2
Allowance for doubtful accounts receivable, write-offs	$ (9.4)	$ (9.2)	$ (10.5)