Derivative Financial Instruments - Schedule of Gain or Loss on the Hedged Items (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on hedged items	$ (2.9)	$ 6.0	$ (11.4)	$ 0.3
Interest Expense
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on hedged items	2.7	(6.0)	11.5	(0.3)
Interest rate swap contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on hedged items	(2.9)	6.0	(11.4)	0.3
Interest rate swap contracts | Interest Expense
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on hedged items	$ 2.7	$ (6.0)	$ 11.5	$ (0.3)