Oil and Gas Properties, Buildings and Equipment (Details) (USD $)	12 Months Ended											12 Months Ended	3 Months Ended	12 Months Ended						12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010	Dec. 31, 2012 Machinery, drilling rigs, and equipment	Dec. 31, 2011 Machinery, drilling rigs, and equipment	Dec. 31, 2012 Building and improvements	Dec. 31, 2011 Building and improvements	Dec. 31, 2012 Vehicles	Dec. 31, 2011 Vehicles	Dec. 31, 2011 East Texas Oil and Gas Properties	Dec. 31, 2011 East Texas Fair Value, Measurements, Nonrecurring Oil and Gas Properties	Dec. 31, 2012 Texas Wells	Dec. 31, 2012 Utah Wells	Dec. 31, 2010 COLORADO Wells	Dec. 31, 2012 3 Drilling Rigs Drilling_rigs	Dec. 31, 2011 3 Drilling Rigs	Oct. 02, 2011 3 Drilling Rigs	Dec. 31, 2012 Unevaluated properties	Dec. 31, 2011 Unevaluated properties	Dec. 31, 2010 Unevaluated properties	Dec. 31, 2011 NYMEX HH
Oil and natural gas:
Proved properties	$ 4,060,106,000	[1]	$ 3,257,321,000	[1]
Unproved properties	236,626,000	[2]	228,486,000	[2]																25,200,000
Oil and natural gas: Proved properties and Unproved properties, gross	4,296,732,000		3,485,807,000
Less accumulated depreciation, depletion and amortization	(1,180,298,000)		(962,154,000)
Oil and natural gas: Proved and Unproved properties, Net	3,116,434,000		2,523,653,000
Oil and natural gas properties (successful efforts basis), buildings and equipment, net	3,128,502,000		2,531,393,000
Capitalized interest costs as component of property costs for development projects (in months)	6
Number of wells encountering mechanical failure																1
Impairment charge related to the write-down of a rig to its fair market value																		4,300,000
Drilling rigs																	3
Proceeds from Sale of Oil and Gas Property and Equipment																	1,800,000
Expense Related to Sale of Long-Lived Asset																	200,000
Gain on sale of assets	1,782,000		0		0												200,000
Future strip, average of the daily settlement prices of futures contracts, percentage decrease																							15.00%
E. Texas Carrying Amount Prior to Impairment												739,300,000
Dry Hole Abandonment and Impairment	19,000,000		5,200,000		1,500,000
Results of Operations, Dry Hole Costs														11,900,000	2,800,000
Exploratory Wells Drilled, Net Nonproductive														4	1
Plugging and Abandonment Expense	4,100,000
Impairment of oil and natural gas properties	79,000		625,564,000		0								625,000,000							100,000	600,000	0
Commerical and other:
Commerical and other, gross	37,408,000		37,209,000			18,131,000	22,509,000	10,110,000	6,894,000	9,167,000	7,806,000							1,400,000	5,700,000
Less accumulated depreciation	(25,340,000)		(29,469,000)
Commercial and other, net	$ 12,068,000		$ 7,740,000

[1] Includes cogeneration facilities.

[2] Unproved properties includes acquisition costs for properties to which proved developed producing and proved undeveloped reserves are also attributed. At December 31, 2012, unproved properties included $25.2 million of acquisition costs for unevaluated properties. The Company assesses these properties annually and recorded impairments of $0.1 million, $0.6 million and $0.0 million for the years ended December 31, 2012, 2011 and 2010, respectively.