Retirement Benefit Plans (Weighted Average Assumptions used to Determine Benefit Obligations) (Details)	Dec. 31, 2016	Dec. 31, 2015
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate (as a percent)	4.01%	4.20%
SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate (as a percent)	3.63%	3.75%
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate (as a percent)	3.27%	3.35%