Fair Value Measurements - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2014 Company Lenders	Mar. 31, 2013	Dec. 31, 2013
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Interest and dividends	$ 274,000	$ 40,000
Mark-to-market gain (loss)	429,000	1,600,000
Allowance for uncollectible receivables	2,500,000		2,500,000
Number of financial institutions included in counter parties	14
Number of secured lenders not in banking credit facility	2
Net derivative asset	$ 3,800,000
Basis Swap | Fair Value, Inputs, Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Number of natural gas basis swap	4