Concentrations - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($)
Unusual Risk or Uncertainty [Line Items]
Maximum amount of credit risk exposure	$ 20,826
GOM Deep Water, Conventional Shelf and Deep Gas Properties [Member]
Unusual Risk or Uncertainty [Line Items]
Production associated with properties	56.00%
Estimated proved reserves derived	99.00%
Appalachian Properties [Member]
Unusual Risk or Uncertainty [Line Items]
Production associated with properties	44.00%
Estimated proved reserves derived	1.00%