Derivative Instrument and Hedging Activities - Open Crude and Natural Gas Derivative Instruments (Parenthetical) (Detail)	3 Months Ended			3 Months Ended
	Mar. 31, 2013	Dec. 31, 2013	Oct. 31, 2013	Mar. 31, 2013 Open Crude Oil Derivative Positions [Member]	Mar. 31, 2013 Open Natural Gas Derivative Positions [Member]	Mar. 31, 2013 2013 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Percentage of collars derivative settled						50.00%
Fixed Price swaps not designated as cash flow hedges		50,000	50,000	9,673	12,840,000
Weighted average fixed price	3.42			94.76	4.34