Oil and Gas Producing Activities (Unaudited) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Property acquisition costs [Abstract]
Unproved	$ 1,965	$ 3,591	$ 2,295
Proved	0	0	0
Exploration costs [Abstract]
Expensed	1,151	9,166	3,233
Capitalized	0	0	0
Development costs	20,219	12,133	6,233
Total costs incurred	23,335	24,890	11,761
Capitalized costs relating to oil and gas producing activities [Abstract]
Unproved oil and gas properties	8,349	7,291
Proved oil and gas properties	82,083	74,376
Gross capitalized cost	90,432	81,667
Accumulated depreciation, depletion and amortization	(57,833)	(55,061)
Net capitalized cost	32,599	26,606
Components of proved oil and gas reserves [Abstract]
Period of average estimated price of proved reserves	12 months
Standardized measure of discounted future net cash flows [Abstract]
Future gross revenues	59,793	73,626	61,311
Future costs- [Abstract]
Lease operating expenses	(16,357)	(19,788)	(17,288)
Development costs	(299)	(2,198)	(1,596)
Future net cash flows before income taxes	43,137	51,640	42,427
Discount at 10% per annum	(17,976)	(19,439)	(16,777)
Discounted future net cash flows before income taxes	25,161	32,201	25,650
Future income taxes, net of discount at 10% per annum	(8,806)	(11,270)	(8,978)
Standardized measure of discounted future net cash flows	16,355	20,931	16,672
Effect of income taxes and discounting on the standardized measure of discounted future net cash flows [Abstract]
Future net cash flows before income taxes	43,137	51,640	42,427
Future income taxes	(15,098)	(18,074)	(14,849)
Future net cash flows	28,039	33,566	27,578
Discount at 10% per annum	(11,684)	(12,635)	(10,906)
Standardized measure of discounted future net cash flows	16,355	20,931	16,672
Principal sources of changes in the standardized measure of discounted future net flows [Abstract]
Beginning of year	20,931	16,672	9,305
Sale of oil and gas reserves	(3,802)	(7,429)	0
Net change in prices and production costs	(5,313)	791	9,435
New field discoveries and extensions, net of future production costs	9,513	18,769	9,068
Sales of oil and gas produced, net of production costs	(8,953)	(7,723)	(7,084)
Net change due to revisions in quantity estimates	(940)	(1,739)	(1,369)
Accretion of discount	1,944	1,678	1,072
Production rate changes and other	511	2,204	213
Net change in income taxes	2,464	(2,292)	(3,968)
End of year	16,355	20,931	16,672
Results of operations for oil and gas producing activities [Abstract]
Revenues	15,954	14,060	11,021
Costs and Expenses [Abstract]
Production	(7,091)	(6,337)	(3,937)
Producing property impairment	(4,699)	(7,105)	(946)
Exploration	(1,151)	(9,166)	(3,233)
Oil and natural gas property sale gain	2,203	2,923	0
Depreciation, depletion and amortization	(8,817)	(8,246)	(4,662)
Operating income (loss) before income taxes	(3,601)	(13,871)	(1,757)
Income tax (expense) benefit	1,060	4,854	615
Operating income (loss)	$ (2,541)	$ (9,017)	$ (1,142)
Crude Oil [Member]
Average Sales Price and Production Costs Per Unit of Production [Line Items]
Average sales prices	93.85	95.85	76.14
Natural Gas [Member]
Average Sales Price and Production Costs Per Unit of Production [Line Items]
Average sales prices	3.51	4.69	5.26
Oil [Member]
Total proved reserves- [Abstract]
Beginning of year	292,000	267,000	242,000
Revisions of previous estimates	29,000	(24,000)	0
Oil and gas reserves sold	(54,000)	(26,000)	0
Extensions, discoveries and other reserve additions	138,000	137,000	79,000
Production	(98,000)	(62,000)	(54,000)
End of year	307,000	292,000	267,000
Components of proved oil and gas reserves [Abstract]
Proved developed reserves	306,000	277,000	240,000
Proved undeveloped reserves	1,000	15,000	27,000
Total proved reserves	307,000	292,000	267,000
Natural Gas [Member]
Total proved reserves- [Abstract]
Beginning of year	9,661,000	7,794,000	7,248,000
Revisions of previous estimates	(507,000)	(520,000)	(832,000)
Oil and gas reserves sold	(104,000)	(2,148,000)	0
Extensions, discoveries and other reserve additions	2,395,000	6,430,000	2,743,000
Production	(2,608,000)	(1,895,000)	(1,365,000)
End of year	8,837,000	9,661,000	7,794,000
Components of proved oil and gas reserves [Abstract]
Proved developed reserves	8,708,000	9,433,000	7,134,000
Proved undeveloped reserves	129,000	228,000	660,000
Total proved reserves	8,837,000	9,661,000	7,794,000