Summary of Significant Accounting Policies (Details) (USD $)	3 Months Ended	6 Months Ended		12 Months Ended		1 Months Ended															6 Months Ended		6 Months Ended							3 Months Ended	6 Months Ended										6 Months Ended		3 Months Ended
	Mar. 31, 2012	Jun. 30, 2013 mi	Jun. 30, 2012	Dec. 31, 2012	Dec. 31, 2011	Aug. 31, 2013 Commodity Contract [Member] bbl MMBTU	Jul. 31, 2013 Commodity Contract [Member] bbl MMBTU Contract	Jun. 30, 2013 Commodity Contract [Member] bbl Contract	Mar. 31, 2013 Commodity Contract [Member] MMBTU	Feb. 28, 2013 Commodity Contract [Member] MMBTU	Jan. 31, 2013 Commodity Contract [Member] MMBTU bbl Contract	Dec. 31, 2012 Commodity Contract [Member] Contract	Jun. 30, 2013 Commodity Contract [Member] Not Designated as Hedging Instrument [Member] Current Assets [Member]	Dec. 31, 2012 Commodity Contract [Member] Not Designated as Hedging Instrument [Member] Current Assets [Member]	Jun. 30, 2013 Commodity Contract [Member] Not Designated as Hedging Instrument [Member] Other Assets [Member]	Dec. 31, 2012 Commodity Contract [Member] Not Designated as Hedging Instrument [Member] Other Assets [Member]	Jun. 30, 2013 Commodity Contract [Member] Not Designated as Hedging Instrument [Member] Current Liabilities [Member]	Dec. 31, 2012 Commodity Contract [Member] Not Designated as Hedging Instrument [Member] Current Liabilities [Member]	Jun. 30, 2013 Commodity Contract [Member] Not Designated as Hedging Instrument [Member] Other Liabilities [Member]	Dec. 31, 2012 Commodity Contract [Member] Not Designated as Hedging Instrument [Member] Other Liabilities [Member]	Jun. 30, 2013 Wells Fargo Bank [Member]	Dec. 31, 2012 Wells Fargo Bank [Member]	Jun. 30, 2013 Revenue [Member]	Jun. 30, 2013 Revenue [Member] Customer Concentration Risk [Member]	Jun. 30, 2013 Accounts Receivable [Member]	Jun. 30, 2013 Accounts Receivable [Member] Product Concentration Risk [Member]	Jun. 30, 2013 Minimum [Member]	Jun. 30, 2013 Minimum [Member] Customer Concentration Risk [Member] Customer	Jun. 30, 2013 Maximum [Member]	Jun. 30, 2013 Maximum [Member] Customer Concentration Risk [Member] Customer	Jun. 30, 2013 Producing Oil and Gas Properties [Member]	Jun. 30, 2012 Producing Oil and Gas Properties [Member]	Jun. 30, 2013 Non-Producing Oil and Gas Properties [Member]	Jun. 30, 2012 Non-Producing Oil and Gas Properties [Member]	Jun. 30, 2013 South Texas Project acreage [Member]	Dec. 31, 2012 South Texas Project acreage [Member]	Jun. 30, 2013 West Texas Project acreage [Member]	Dec. 31, 2012 West Texas Project acreage [Member]	Jun. 30, 2013 Napoleonville, Louisiana acreage [Member]	Dec. 31, 2012 Napoleonville, Louisiana acreage [Member]	Jun. 30, 2013 Other acreage areas [Member]	Dec. 31, 2012 Other acreage areas [Member]	Jun. 30, 2013 Onshore leasehold [Member]
Nature of Operations and Principles of Consolidation [Abstract]
Primary area of operation (in miles)		1,000
Components of prepayments and other [Abstract]
Cash collateral deposits for commodity purchases		$ 5,186,000		$ 5,000,000
Insurance premiums		2,879,000		1,872,000
Commodity imbalances and futures		14,000		353,000
Rents, license and other		752,000		867,000
Prepayments, total		8,831,000		8,092,000
Property, Plant and Equipment [Line Items]
Exploratory drilling costs		0
Property and equipment, useful life																											3 years		20 years														3 years
Capitalized costs for non producing oil and gas leasehold interests specified as percentage of total costs (in hundredths)																																	4.00%
Total Non-producing Leasehold Costs		4,464,000		4,095,000																															3,630,000	3,263,000	154,000	180,000	323,000	323,000	357,000	329,000
Fair value measurements for producing oil and gas properties that were subject to fair value impairment [Abstract]
Balance December 31, 2012																																									329,000
Property additions																																									128,000
Impairment		(242,000)	(629,000)																												(142,000)	(71,000)	(100,000)	(558,000)							(100,000)
Balance June 30, 2013																																									357,000
Pre-tax gain on sale of truck and equipment	1,269,000
Cash Deposits and Other Assets [Abstract]
Insurance collateral deposits		3,078,000		3,413,000
State collateral deposits		170,000		170,000
Materials and supplies		594,000		616,000
Cash deposits and other		3,842,000		4,199,000
Revenue Recognition [Abstract]
Increase in the entity's reported revenue		714,489,000	717,826,000
Concentration of Credit Risk [Line Items]
Concentration risk, percentage (in hundredths)																								50.00%		95.00%
Concentration risk, additional characteristic																								Large crude oil refining concerns		Crude oil and natural gas marketing activities
Number of customers																												2		3
Maximum percentage of US demand supplied by company (in hundredths)		1.00%
Percentage of revenues from one customer which loss would not have material effect (in hundredths)																							10.00%
Industry practice payment of receivables																									25
Letter of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity																					60,000,000
Standby letters of credit issued																					15,400,000	21,900,000
Covenant terms																					Such restrictions included the maintenance of a combined 1.1 to 1.0 current ratio and the maintenance of positive net earnings excluding inventory valuation changes, as defined, among other restrictions. The Company is currently in compliance with all such financial covenants.
Current ratio																					1.1
Statement of Cash Flows [Abstract]
Interest paid		23,000	3,000
Income taxes paid		7,739,000	3,301,000
Non-cash investing activities for property and equipment		2,468,000	2,627,000	2,419,000	4,070,000
Earnings Per Share [Abstract]
Weighted average number of shares outstanding (in shares)		4,217,596		4,217,596
Fair Value Forward Hydrocarbon Commodity Contracts at Gross Valuation [Abstract]
Asset Derivatives													68,000	688,000	0	0	0	0	0	0
Liability Derivatives													0	0	0	0	(64,000)	682,000	0	0
Less Counterparty Offsets													0	(270,000)	0	0	0	(270,000)	0	0
As Reported Fair Value Contracts													$ 68,000	$ 418,000	$ 0	$ 0	$ (64,000)	$ 412,000	$ 0	$ 0
Number of purchase and sales contracts held								25				24
Volume of crude oil purchased and sold per day under derivative contracts (in barrels)						170	170	200			900
Volume of natural gas purchased and sold per day under derivative contracts (in mmbtu)						930,000	7,841,000		41,000	1,000	172,000