Retirement Benefits (Components Of Net Periodic (Benefit Credit) Benefit Cost) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2.6	$ 2.9	$ 7.6	$ 8.6
Interest cost	16.6	17.3	49.9	51.9
Expected return on assets	(36.9)	(36.7)	(110.7)	(110.1)
Recognized actuarial loss	5.4	4.5	16.3	13.2
Settlement loss	2.9	1.1	6.7	6.7
Amortization of prior service credit	(0.1)	(0.2)	(0.3)	(0.4)
Net periodic (benefit credit) benefit cost	(9.5)	(11.1)	(30.5)	(30.1)
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.3	0.3	1.0	1.1
Interest cost	5.2	5.6	15.6	16.8
Expected return on assets	(5.7)	(5.6)	(17.0)	(16.8)
Recognized actuarial loss	2.9	3.1	8.6	9.3
Settlement loss	0.0	0.0	0.0	0.0
Amortization of prior service credit	(3.4)	(3.4)	(10.2)	(10.3)
Net periodic (benefit credit) benefit cost	$ (0.7)	$ 0.0	$ (2.0)	$ 0.1