Income Taxes (Narrative) (Details)	4 Months Ended	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)
Income Taxes [Line Items]
Additions, reductions or settlements in unrecognized tax benefits	$ 0
Uncertain tax positions	0	$ 0
Deferred tax assets, net operating loss carryforwards	8,900,000	$ 8,900,000
Income Tax Examination, Description		We are subject to income taxes in the U.S. federal jurisdiction and various states. Tax regulations within each jurisdiction are subject to the interpretations of the related tax laws and regulations and require significant judgment to apply. We are no longer subject to U.S. federal, state, and local, or non-U.S. income tax examinations by tax authorities for the years before 2013.
General Business
Income Taxes [Line Items]
Tax credit carryforward relating to enhanced oil recovery	1,300,000	$ 1,300,000
Latest Tax Year | General Business
Income Taxes [Line Items]
Tax credit carryforward relating to enhanced oil recovery, expiration year		2036
Federal
Income Taxes [Line Items]
Net operating loss carryforward	23,100,000	$ 23,100,000
Federal | Earliest Tax Year
Income Taxes [Line Items]
Net operating loss carryforwards, expiration year		2036
State
Income Taxes [Line Items]
Net operating loss carryforward	$ 17,800,000	$ 17,800,000
State | Earliest Tax Year
Income Taxes [Line Items]
Net operating loss carryforwards, expiration year		2031
State | Latest Tax Year
Income Taxes [Line Items]
Net operating loss carryforwards, expiration year		2036