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Commitments and Contingencies (Allowance For Doubtful Debts) (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Commitments and Contingencies [Abstract]      
Balance at beginning of period $ 591 $ 591 $ 755
Provision 16
Reversal of provision (180)
Write-off of provision (181)
Balance at end of period $ 410 $ 591 $ 591