Defined Benefit Pension Plans (Weighted-Average Assumptions Used) (Details)	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Qualified Pension Plan [Member]
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Equivalent single discount rate for benefit obligations	4.18%	4.48%
Equivalent single discount rate for service cost	4.29%	4.63%
Equivalent single discount rate for interest cost	3.73%	3.88%
Expected long-term return on plan assets	6.75%	6.75%
Rate of compensation increase	3.75%	3.75%
Non-Qualified Retirement Plans [Member]
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Equivalent single discount rate for benefit obligations	3.96%	4.19%
Equivalent single discount rate for service cost	4.25%	4.59%
Equivalent single discount rate for interest cost	3.36%	3.44%
Rate of compensation increase	3.75%	3.75%