Derivative Activities - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($) MMBTU / d bbl Counterparty Institution	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Derivative [Line Items]
Number of financial institutions with whom we conduct derivative activities | Institution	17
Number of secured lenders not in banking credit facility | Counterparty	4
Gain (Loss) Recognized in Income (Ineffective Portion)	$ 0	$ 0	$ (2,930)
Not Designated as Hedging Instrument
Derivative [Line Items]
Accumulated other comprehensive income, net gains	103,600
Accumulated other comprehensive income, net gains, after tax	63,200
Designated as Hedging Instrument
Derivative [Line Items]
Gains (Losses) in oil and gas sales related to settled hedging transactions		$ 10,200	$ 116,500
Derivatives Excluding Basis Swaps
Derivative [Line Items]
Derivative assets liabilities at fair value net	283,300
Natural Gas | Basis Swaps
Derivative [Line Items]
Derivative assets liabilities at fair value net	$ 5,500
Volume Hedged | MMBTU / d	53,365,000
Propane | Basis Swaps
Derivative [Line Items]
Derivative assets liabilities at fair value net	$ (1,100)
Volume Hedged | bbl	4,679