Other Comprehensive Income (OCI) and Fair Value Measurements OCI (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Assets, Fair Value Disclosure, Recurring	$ 0.0		$ 0.0		$ 0.0
Liabilities, Fair Value Disclosure, Recurring	0.0		0.0		$ 0.0
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			4,326.7	$ 4,102.3
Interest expense	48.4	$ 43.1	136.4	134.2
Pension and other postretirement benefit costs	0.6	0.0	2.3	(4.3)
Ending balance	4,468.1	4,295.6	4,468.1	4,295.6
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(7.2)	(9.6)	(8.4)	(10.8)
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months			(2.4)
Pension and other postretirement benefit costs	0.0		0.0	0.0
Ending balance	(6.6)	(9.0)	(6.6)	(9.0)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest expense	0.6	0.6	1.8	1.8
Accumulated Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(74.2)	(66.3)	(75.9)	(62.0)
Pension and other postretirement benefit costs	0.6		2.3	(4.3)
Ending balance	(73.6)	(66.3)	(73.6)	(66.3)
Accumulated Defined Benefit Plans Adjustment | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest expense	0.0	0.0	0.0	0.0
AOCI Attributable to Parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(81.4)	(75.9)	(84.3)	(72.8)
Pension and other postretirement benefit costs	0.6		2.3	(4.3)
Ending balance	(80.2)	(75.3)	(80.2)	(75.3)
AOCI Attributable to Parent | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest expense	$ 0.6	$ 0.6	$ 1.8	$ 1.8