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Pension Benefit and Retirement Health and Life Insurance Benefits (Assumptions Used) (Details)
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]    
Discount rate 4.25% 4.00%
Pension Benefits    
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]    
Discount rate 4.25% 4.00%
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]    
Discount rate 4.00% 4.75%
Expected long-term rate of return on plan assets 6.50% 7.50%
Retirement Health and Life Insurance Benefits    
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]    
Discount rate 3.00% 3.00%
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]    
Discount rate 3.00% 3.25%
Expected long-term rate of return on plan assets 0.00% 0.00%