Retirement Benefits (Schedule of Defined Benefit Plan Amounts Recognized in Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2012
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net after tax unamortized periodic pension cost	$ (5,081,134)	$ (4,633,208)
Net pension asset
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net after tax unamortized periodic pension cost	$ 0	$ 0	$ 0	$ 6,651