Supplementary Financial Information for Oil and Gas Producing Activities (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012 acre	Dec. 31, 2011	Dec. 31, 2010
Supplementary Financial Information for Oil and Gas Producing Activities
Area of land (in acres)									3,800
Area of land under a lease (in acres)									538
Results of Operations
Revenues	$ 1,671	$ 1,558	$ 1,769	$ 2,123	$ 3,032	$ 3,524	$ 3,458	$ 2,864	$ 7,121	$ 12,878	$ 7,425
Production and operating costs									1,891	2,269	1,421
Depreciation and depletion									1,291	1,402	1,172
Results of operations before income taxes									3,939	9,207	4,832
Income tax expense									1,044	2,664	1,410
Results of operations (excluding corporate overhead and interest costs)									2,895	6,543	3,422
Costs Incurred
Development costs incurred									81	927	2,204
Capitalized asset retirement costs										3	3
Capitalized Costs
Natural gas properties - proved	18,301				18,220				18,301	18,220	17,295
Less: accumulated depreciation and depletion	7,294				5,997				7,294	5,997	4,593
Net capitalized costs for natural gas properties	11,007				12,223				11,007	12,223	12,702
Unaudited standardized measure of discounted future net cash flows
Future estimated gross revenues									57,882	120,920	102,198
Future estimated production and development costs									(23,905)	(32,138)	(31,406)
Future estimated net revenues									33,977	88,782	70,792
Future estimated income tax expense									(9,193)	(25,627)	(20,174)
Future estimated net cash flows									24,784	63,155	50,618
10% annual discount for estimated timing of cash flows									(12,020)	(33,207)	(24,162)
Standardized measure of discounted future estimated net cash flows									12,764	29,948	26,456
Changes in standardized measure of discounted future net cash flows
Standardized measure - beginning of year				29,948				26,456	29,948	26,456	23,076
Net change in sales prices and production costs									(7,067)	2,403	8,689
Sales of natural gas produced, net of production costs									(5,230)	(7,805)	(5,992)
Extensions and discoveries, net of related costs											1,737
Future development costs											(716)
Net change due to changes in quantity estimates									(5,863)	4,086	(5,488)
Previously estimated development costs incurred									116	925	1,549
Net change in income taxes									7,419	(1,609)	(1,237)
Accretion of discount									1,603	3,211	2,962
Timing of production of reserves and other									(8,162)	2,281	1,876
Standardized measure - end of year	$ 12,764				$ 29,948				$ 12,764	$ 29,948	$ 26,456
Natural Gas (BCF)
Reserve Quantities
Price (in dollars per Mcf or Bbl)									2.87	4.46	4.52
Proved reserves utilizing year-end prices	10,100.0				10,200.0				10,100.0	10,200.0	13,100.0
Changes in proved reserves
Proved reserves - beginning of year				10,300.0				12,300.0	10,300.0	12,300.0	13,300.0
Revisions of previous estimates									(800.0)	(800.0)	(600.0)
Extensions and discoveries											400
Production									(1,200.0)	(1,200.0)	(800.0)
Proved reserves - end of year	8,300.0				10,300.0				8,300.0	10,300.0	12,300.0
Proved developed reserves - end of year	8,300.0				10,300.0				8,300.0	10,300.0	11,700.0
Natural Gas Liquids (MMBLS)
Reserve Quantities
Price (in dollars per Mcf or Bbl)									30.27	49.58	38.71
Proved reserves utilizing year-end prices	1.5				1.5				1.5	1.5	1.3
Changes in proved reserves
Proved reserves - beginning of year				1.5				1.2	1.5	1.2	1.8
Revisions of previous estimates									(0.3)	0.5	(0.6)
Production									(0.1)	(0.2)
Proved reserves - end of year	1.1				1.5				1.1	1.5	1.2
Proved developed reserves - end of year	1.1				1.5				1.1	1.5	1.2