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Employee Benefit Plans (Schedule of Assumptions used to Determine Net Pension Cost) (Details)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Retirement Benefits [Abstract]      
Weighted average discount rate 4.25% 4.50% 4.00%
Rate of increase in compensation levels [1]
Expected long-term rate of return on assets 6.50% 6.75% 6.75%
[1] 6.0% graded down to 3.25% over the first seven years of service