Summary of Significant Accounting Policies (Details)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2015 USD ($) mi² Contract	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($) mi² BarrelsofOilPerDay Customer Contract shares	Jun. 30, 2014 USD ($)	Dec. 31, 2014 USD ($) BarrelsofOilPerDay Contract shares	Dec. 31, 2013 USD ($)
Nature of Operations and Principles of Consolidation [Abstract]
Primary area of operation (in square miles) | mi²	1,000		1,000
Components of Prepayments and Other [Abstract]
Cash collateral deposits for commodity purchases	$ 7,760,000		$ 7,760,000		$ 7,872,000
Insurance premiums	2,818,000		2,818,000		2,316,000
Rents, license and other	577,000		577,000		752,000
Prepayments, total	11,155,000		11,155,000		10,940,000
Property, Plant and Equipment [Line Items]
Total Non-producing Leasehold Costs	839,000		839,000		959,000
Fair value measurements for oil and gas properties that were subject to fair value impairment [Abstract]
Impairment			623,000	$ 405,000
Cash Deposits and Other Assets [Abstract]
Insurance collateral deposits	4,886,000		4,886,000		4,536,000
State collateral deposits	174,000		174,000		155,000
Materials and supplies	349,000		349,000		307,000
Cash deposits and other	5,409,000		5,409,000		4,998,000
Revenue Recognition [Abstract]
Increase in the entity's reported revenue	136,440,000	$ 347,907,000	$ 266,663,000	782,601,000
Concentration of Credit Risk [Line Items]
Maximum percentage of US demand supplied by company (in hundredths)			1.00%
Statement of Cash Flows [Abstract]
Interest paid			$ 4,000	0
Income taxes paid			1,607,000	8,253,000
Non-cash investing activities for property and equipment			$ 53,000	846,000	$ 1,137,000	$ 1,507,000
Earnings Per Share [Abstract]
Weighted average number of shares outstanding (in shares) | shares			4,217,596		4,217,596
Minimum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, useful life			3 years
Maximum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, useful life			20 years
Customer Concentration Risk [Member] | Minimum [Member]
Concentration of Credit Risk [Line Items]
Number of customers | Customer			3
Customer Concentration Risk [Member] | Maximum [Member]
Concentration of Credit Risk [Line Items]
Number of customers | Customer			4
Producing Oil and Gas Properties [Member]
Fair value measurements for oil and gas properties that were subject to fair value impairment [Abstract]
Impairment	$ 4,000	0	$ 207,000	0
Non-Producing Oil and Gas Properties [Member]
Property, Plant and Equipment [Line Items]
Capitalized costs for non-producing oil and gas leasehold interests specified as percentage of total costs (in hundredths)	4.00%		4.00%
Fair value measurements for oil and gas properties that were subject to fair value impairment [Abstract]
Impairment	$ 411,000	$ 312,000	$ 416,000	405,000
South Texas Project acreage [Member]
Property, Plant and Equipment [Line Items]
Total Non-producing Leasehold Costs	358,000		358,000		$ 357,000
Napoleonville, Louisiana acreage [Member]
Property, Plant and Equipment [Line Items]
Total Non-producing Leasehold Costs	49,000		49,000		48,000
North Dakota and other acreage areas [Member]
Property, Plant and Equipment [Line Items]
Total Non-producing Leasehold Costs	432,000		432,000		554,000
Fair value measurements for oil and gas properties that were subject to fair value impairment [Abstract]
Net book value January 1			554,000	$ 411,000	411,000
Property additions			65,000		580,000
Impairment			(187,000)		(437,000)
Net book value end of period	432,000		$ 432,000		554,000	$ 411,000
Onshore Leasehold [Member]
Property, Plant and Equipment [Line Items]
Onshore Leasehold Period			3 years
Wells Fargo Bank [Member]
Letter of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	60,000,000		$ 60,000,000
Standby letters of credit issued	$ 1,000,000		$ 1,000,000		$ 15,300,000
Current ratio			1.1
Commodity Contract [Member]
Fair Value Forward Hydrocarbon Commodity Contracts at Gross Valuation [Abstract]
Number of contracts held | Contract	5		5		3
Commodity Contract [Member] | July 2015 through September 2015 [Member]
Fair Value Forward Hydrocarbon Commodity Contracts at Gross Valuation [Abstract]
Volume committed per day under commodity purchase and sale contract (in barrels per day) | BarrelsofOilPerDay			161
Commodity Contract [Member] | October 2015 through December 31, 2015 [Member]
Fair Value Forward Hydrocarbon Commodity Contracts at Gross Valuation [Abstract]
Volume committed per day under commodity purchase and sale contract (in barrels per day) | BarrelsofOilPerDay			129
Commodity Contract [Member] | July 2015 through March 2016 [Member]
Fair Value Forward Hydrocarbon Commodity Contracts at Gross Valuation [Abstract]
Volume committed per day under commodity purchase and sale contract (in barrels per day) | BarrelsofOilPerDay			65
Commodity Contract [Member] | January and February 2015 [Member]
Fair Value Forward Hydrocarbon Commodity Contracts at Gross Valuation [Abstract]
Volume committed per day under commodity purchase and sale contract (in barrels per day) | BarrelsofOilPerDay					294
Commodity Contract [Member] | March through December 2015 [Member]
Fair Value Forward Hydrocarbon Commodity Contracts at Gross Valuation [Abstract]
Volume committed per day under commodity purchase and sale contract (in barrels per day) | BarrelsofOilPerDay					129
Commodity Contract [Member] | Not Designated as Hedging Instrument [Member] | Current Assets [Member]
Fair Value Forward Hydrocarbon Commodity Contracts at Gross Valuation [Abstract]
Asset Derivatives	$ 410,000		$ 410,000		$ 1,332,000
Liability Derivatives	0		0		0
Less Counterparty Offsets	(7,000)		(7,000)		(396,000)
As Reported Fair Value Contracts	403,000		403,000		936,000
Commodity Contract [Member] | Not Designated as Hedging Instrument [Member] | Other Assets [Member]
Fair Value Forward Hydrocarbon Commodity Contracts at Gross Valuation [Abstract]
Asset Derivatives	0		0		0
Liability Derivatives	0		0		0
Less Counterparty Offsets	0		0		0
As Reported Fair Value Contracts	0		0		0
Commodity Contract [Member] | Not Designated as Hedging Instrument [Member] | Current Liabilities [Member]
Fair Value Forward Hydrocarbon Commodity Contracts at Gross Valuation [Abstract]
Asset Derivatives	0		0		0
Liability Derivatives	367,000		367,000		1,339,000
Less Counterparty Offsets	(7,000)		(7,000)		(396,000)
As Reported Fair Value Contracts	360,000		360,000		943,000
Commodity Contract [Member] | Not Designated as Hedging Instrument [Member] | Other Liabilities [Member]
Fair Value Forward Hydrocarbon Commodity Contracts at Gross Valuation [Abstract]
Asset Derivatives	0		0		0
Liability Derivatives	0		0		0
Less Counterparty Offsets	0		0		0
As Reported Fair Value Contracts	$ 0		$ 0		$ 0
Revenue [Member]
Concentration of Credit Risk [Line Items]
Percentage of revenues from one customer which loss would not have material effect (in hundredths)			10.00%
Revenue [Member] | Customer Concentration Risk [Member]
Concentration of Credit Risk [Line Items]
Concentration risk, percentage (in hundredths)			50.00%
Accounts Receivable [Member]
Concentration of Credit Risk [Line Items]
Industry practice payment of receivables			20 days
Accounts Receivable [Member] | Product Concentration Risk [Member]
Concentration of Credit Risk [Line Items]
Concentration risk, percentage (in hundredths)			95.00%