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Retirement and Postretirement Plans Retirement and Postretirment Plans (Assumptions) (Details)
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Qualified Plan [Member]    
Discount Yield (as a percent) 3.78% 3.22%
Discount rate (as a percent) 3.88%  
Pension Costs [Member]    
Discount rate (as a percent)   3.91%
Long-Duration Contracts, Assumptions by Product and Guarantee, Estimated Average Investment Yield 3.00% 6.00%