Fair Value Measurements - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 Companies	Sep. 30, 2011	Dec. 31, 2011
Fair Value Measurements Of Financial Instruments [Line Items]
Interest and dividends	$ 122,000	$ 84,000	$ 279,000	$ 179,000
Mark-to-market gain (loss)	3,800,000	(7,900,000)	5,700,000	(6,600,000)
Proceeds from sale of oil and gas property and equipment			32,082,000	40,264,000
Allowance for uncollectible receivables	1,600,000		1,600,000		4,000,000
Number of financial institutions included in counter parties			16
Number of counter parties not included in bank credit facility			2
Net Derivative Asset	12,700,000		12,700,000
Gulf Coast [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Impairment on oil and gas properties				7,500,000
East Texas [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Impairment on oil and gas properties				31,200,000
Proceeds from sale of oil and gas property and equipment				10,500,000
Surface Property [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Impairment of long lived assets	$ 1,300,000