Retirement Benefits (Net Amounts Included In Accumulated Other Comprehensive Loss That Have Not Been Recognized As Components Of Net Periodic Benefit Costs) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	$ 655.8	$ 635.0
Prior service cost (credit)	0.5	(0.1)
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	655.8	635.0
Prior service cost (credit)	0.5	(0.1)
Net amount before tax at December 31	656.3	634.9
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	146.6	162.7
Prior service cost (credit)	(59.7)	(73.5)
Net amount before tax at December 31	$ 86.9	$ 89.2