Retirement Benefits (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Defined Benefit Plan [Abstract]
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 0.2	$ 0.3	$ 0.2	$ 0.3