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Income Taxes (Narrative) (Details) - USD ($)
$ in Thousands
3 Months Ended 12 Months Ended
Mar. 31, 2018
Dec. 31, 2017
Mar. 31, 2017
Dec. 31, 2017
Income Taxes [Abstract]        
Statutory U.S. federal income tax rate 21.00%   35.00% 35.00%
Income tax expense/(benefit) from tax rate change $ 399 $ (6,047)