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Employee Benefit Plans (Assumptions Used in the Measurement of Net Periodic Cost) (Details)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Discount rate for benefit obligations 4.22% 4.47% 4.15%
Expected return on plan assets 5.75% 6.11% 6.24%
Rate for interest on benefit obligations 3.51%    
Postretirement Benefit Plan [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Discount rate for benefit obligations 4.18% 4.39% 4.03%
Rate for interest on benefit obligations 3.48%    
Discount rate for service cost 4.55%