Other Postretirement Employee Benefit Plans (Components Of Net Periodic Benefit Cost) (Details) - Other postretirement benefits - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0.7	$ 0.7
Interest cost	5.6	6.6
Amortization of net gain	(0.1)	0.0
Amortization of prior service credit	(3.1)	(3.1)
Net periodic pension cost	$ 3.1	$ 4.2