Retirement Benefits (Reconciliation Of The Beginning And Ending Balances Of Plan Assets Measured At Fair Value Using Level III Inputs) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 548.3	$ 587.7	$ 583.9
Actual return on plan assets, relating to assets still held at the reporting date	(18.4)	4.4	22.9
Purchases	17.9	20.0	25.1
Sales	(25.1)	(63.8)	(44.2)
Ending balance	522.7	548.3	587.7
Partnership Interests [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	122.2	160.3	177.7
Actual return on plan assets, relating to assets still held at the reporting date	(5.9)	(5.4)	2.2
Purchases	10.9	8.4	15.6
Sales	(8.6)	(41.1)	(35.2)
Ending balance	118.6	122.2	160.3
Insurance Company Contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	187.7	197.4	202.5
Actual return on plan assets, relating to assets still held at the reporting date	(5.7)	1.4	(5.6)
Purchases	7.0	11.6	9.5
Sales	(14.8)	(22.7)	(9.0)
Ending balance	174.2	187.7	197.4
Life Insurance Contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	238.4	230.0	203.7
Actual return on plan assets, relating to assets still held at the reporting date	(6.8)	8.4	26.3
Purchases	0.0	0.0	0.0
Sales	(1.7)	0.0	0.0
Ending balance	$ 229.9	$ 238.4	$ 230.0