Retirement Benefits (Reconciliation Of The Benefit Obligation) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Pension Benefits [Member]
Reconciliation of benefit obligation
Benefit obligation at beginning of year	$ 1,833.3	$ 1,914.4
Service cost	11.6	13.1	$ 13.0
Interest cost	68.5	68.2	74.1
Plan amendments	0.0	0.8
Actuarial loss (gain)	32.2	(41.2)
Benefits paid	(120.7)	(122.0)
Benefit obligation at end of year	1,824.9	1,833.3	1,914.4
Other Benefits [Member]
Reconciliation of benefit obligation
Benefit obligation at beginning of year	578.7	646.6
Service cost	1.6	2.1	3.2
Interest cost	22.4	23.4	26.3
Plan amendments	0.0	0.0
Actuarial loss (gain)	(4.2)	(58.1)
Benefits paid	(33.3)	(35.3)
Benefit obligation at end of year	$ 565.2	$ 578.7	$ 646.6