Accumulated Other Comprehensive Income (Loss) Accumulated Other Comprehensive Income/(Loss) Reclassifications out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Sep. 30, 2017	Sep. 30, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Derivative Instruments, Loss Reclassified from Accumulated OCI into Income, Effective Portion	$ (5.3)			$ (4.6)			$ (18.1)	$ (18.0)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax	2.0			1.8			6.9	7.0
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(3.3)	$ (3.1)	$ (4.7)	(2.8)	$ (2.9)	$ (5.3)	11.2	11.0
Other Comprehensive Income (Loss), Reclassification Adjustment on Pension and Other Post Retirement Obligations included in Net Income, before Tax	(3.3)			(1.6)			(6.2)	(4.8)
Other Comprehensive Income (Loss), Reclassification Adjustment on Pension and Other Post Retirement Obligations included in Net Income, Tax	1.3			0.6			2.6	1.8
Other Comprehensive Income (Loss), Reclassification Adjustment on Pension and Other Post Retirement Obligations included in Net Income, Net of Tax	(2.0)			(1.0)			(3.6)	(3.0)
Amounts Reclassifed from Accumulated Other Comprehensive Income, Net of Tax	$ (5.3)			$ (3.8)			$ (14.8)	$ (14.0)