Summary of Accounting Policies - Allowance for Doubtful Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Activity in allowance for doubtful accounts
Balance at the Beginning of the period	$ 5.1	$ 6.5	$ 3.9
Increase (decrease) to reserve	1.4	(0.5)	1.2
Amounts acquired	0.6	0.0	2.0
Amounts written off	(0.5)	(0.9)	(0.6)
Balance at the end of the period	$ 6.6	$ 5.1	$ 6.5