Concentrations - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013
Unusual Risk or Uncertainty [Line Items]
Maximum amount of credit risk exposure	$ 74,273
Gulf Coast Basin Conventional Shelf and deep gas Properties [Member]
Unusual Risk or Uncertainty [Line Items]
Production associated with properties	49.00%
Estimated proved reserves derived	16.00%
Deep Water Properties [Member]
Unusual Risk or Uncertainty [Line Items]
Production associated with properties	25.00%
Estimated proved reserves derived	29.00%
Appalachian Properties [Member]
Unusual Risk or Uncertainty [Line Items]
Production associated with properties	26.00%
Estimated proved reserves derived	55.00%