Accumulated Other Comprehensive Income (Loss) - Components of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ 430.0	$ 119.3	$ 384.4	$ 114.5
Foreign currency translation adjustment	0.1	0.3	1.2	(1.8)
Amortization related to derivatives securities, before tax	0.8	0.8	1.6	1.5
Tax impact	(0.2)	(0.2)	(0.4)	(0.4)
Total other comprehensive income (loss)	0.7	0.9	2.4	(0.7)
Ending balance	863.9	152.6	863.9	152.6
Foreign currency translation adjustment
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	5.5	0.7	4.4	2.8
Foreign currency translation adjustment	0.1	0.3	1.2	(1.8)
Amortization related to derivatives securities, before tax	0.0	0.0	0.0	0.0
Tax impact	0.0	0.0	0.0	0.0
Total other comprehensive income (loss)	0.1	0.3	1.2	(1.8)
Ending balance	5.6	1.0	5.6	1.0
Valuation and amortization of derivative securities
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(17.4)	(19.8)	(18.0)	(20.3)
Foreign currency translation adjustment	0.0	0.0	0.0	0.0
Amortization related to derivatives securities, before tax	0.8	0.8	1.6	1.5
Tax impact	(0.2)	(0.2)	(0.4)	(0.4)
Total other comprehensive income (loss)	0.6	0.6	1.2	1.1
Ending balance	(16.8)	(19.2)	(16.8)	(19.2)
AOCI Including Portion Attributable to Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(11.9)	(19.1)	(13.6)	(17.5)
Ending balance	$ (11.2)	$ (18.2)	$ (11.2)	$ (18.2)