Supplementary Financial Information for Oil and Gas Producing Activities (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013 acre	Dec. 31, 2012	Dec. 31, 2011
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	$ 1,443	$ 1,401	$ 1,488	$ 1,430	$ 1,671	$ 1,558	$ 1,769	$ 2,123	$ 5,762	$ 7,121	$ 12,878
Production and operating costs									1,920	1,891	2,269
Depreciation and depletion									955	1,291	1,402
Results of operations before income taxes									2,887	3,939	9,207
Income tax expense									736	1,044	2,664
Results of operations (excluding corporate overhead and interest costs)									2,151	2,895	6,543
Costs Incurred
Development costs incurred									58	81	927
Capitalized asset retirement costs											3
Capitalized Costs
Natural gas properties - proved	18,359				18,301				18,359	18,301	18,220
Less: accumulated depreciation and depletion	8,256				7,294				8,256	7,294	5,997
Net capitalized costs for natural gas properties	10,103				11,007				10,103	11,007	12,223
Unaudited standardized measure of discounted future net cash flows
Future estimated gross revenues									61,873	57,882	120,920
Future estimated production and development costs									(24,276)	(23,905)	(32,138)
Future estimated net revenues									37,597	33,977	88,782
Future estimated income tax expense									(10,286)	(9,193)	(25,627)
Future estimated net cash flows									27,311	24,784	63,155
10% annual discount for estimated timing of cash flows									(13,733)	(12,020)	(33,207)
Standardized measure of discounted future estimated net cash flows									13,578	12,764	29,948
Changes in standardized measure of discounted future net cash flows
Standardized measure - beginning of year				12,764				29,948	12,764	29,948	26,456
Net change in sales prices and production costs									4,227	(7,067)	2,403
Sales of natural gas produced, net of production costs									(4,046)	(5,230)	(7,805)
Net change due to changes in quantity estimates									430	(5,863)	4,086
Previously estimated development costs incurred									56	116	925
Net change in income taxes									(380)	7,419	(1,609)
Accretion of discount									1,486	1,603	3,211
Timing of production of reserves and other									(959)	(8,162)	2,281
Standardized measure - end of year	$ 13,578				$ 12,764				$ 13,578	$ 12,764	$ 29,948
Natural Gas (BCF)
Reserve Quantities
Price (in dollars per Mcf or Bbl)									3.88	2.87	4.46
Changes in proved reserves
Proved reserves - beginning of year				8,300.0				10,300.0	8,300.0	10,300.0	12,300.0
Revisions of previous estimates										(800.0)	(800.0)
Production									(700.0)	(1,200.0)	(1,200.0)
Proved reserves - end of year	7,600.0				8,300.0				7,600.0	8,300.0	10,300.0
Proved developed reserves - end of year	7,600.0				8,300.0				7,600.0	8,300.0	10,300.0
Natural Gas Liquids (MMBLS)
Reserve Quantities
Price (in dollars per Mcf or Bbl)									29.95	30.27	49.58
Changes in proved reserves
Proved reserves - beginning of year				1.1				1.5	1.1	1.5	1.2
Revisions of previous estimates									0.1	(0.3)	0.5
Production									(0.1)	(0.1)	(0.2)
Proved reserves - end of year	1.1				1.1				1.1	1.1	1.5
Proved developed reserves - end of year	1.1				1.1				1.1	1.1	1.5