Accumulated Other Comprehensive Income - Components of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ 8.4	$ 172.0	$ 134.2	$ 127.3
Ending balance	21.8	149.1	21.8	149.1
Foreign currency translation adjustment
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	2.3	4.3	1.8	3.5
Foreign currency translation adjustment	0.6	1.6	0.1	0.8
Other comprehensive income (loss)	(0.6)	(1.6)	(0.1)	(0.8)
Ending balance	1.7	2.7	1.7	2.7
Valuation and amortization of derivative securities
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(22.1)	(24.5)	(22.7)	(25.1)
Amortization related to derivative securities, before tax	(0.8)	0.7	1.5	(1.4)
AOCI Tax, Attributable to Parent	(0.2)	(0.1)	(0.3)	(0.2)
Other comprehensive income (loss)	0.6	0.6	1.2	1.2
Ending balance	(21.5)	(23.9)	(21.5)	(23.9)
AOCI Including Portion Attributable to Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(19.8)	(20.2)	(20.9)	(21.6)
Foreign currency translation adjustment	0.6	1.6	0.1	0.8
Amortization related to derivative securities, before tax	(0.8)	0.7	1.5	1.4
AOCI Tax, Attributable to Parent	(0.2)	(0.1)	(0.3)	(0.2)
Other comprehensive income (loss)	0.0	(1.0)	1.1	0.4
Ending balance	$ (19.8)	$ (21.2)	$ (19.8)	$ (21.2)