Organization and Accounting Policies (Assets and Liabilities Measured on Recurring Basis) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset commodity	$ 1,956	$ 3,520
Assets	1,956	3,520
SARs liability	1,777	1,007
SARs liability	421	625
Liabilities	2,198	1,632
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset commodity	1,956	3,520
Assets	1,956	3,520
SARs liability	1,777	1,007
SARs liability	421	625
Liabilities	$ 2,198	$ 1,632