Derivative Instruments--Derivatives Outstanding (Details)	Dec. 31, 2013 bbl
Swaps | Derivatives Maturing In 2014 | Crude Oil Derivative
Derivative [Line Items]
Volume of derivative instruments held	961,000
Weighted average fixed price per unit, swaps	93.50
Swaps | Derivatives Maturing In 2014 | Natural Gas Derivative
Derivative [Line Items]
Volume of derivative instruments held	21,100,000
Weighted average fixed price per unit, swaps	4.03
Swaps | Derivatives maturing in 2015 | Natural Gas Derivative
Derivative [Line Items]
Volume of derivative instruments held	16,800,000
Weighted average fixed price per unit, swaps	4.21
Costless Collars | Derivatives Maturing In 2014 | Crude Oil Derivative
Derivative [Line Items]
Volume of derivative instruments held	2,400,000
Weighted average fixed price per Bbl, sold puts	75.50
Weighted average fixed price per Bbl, purchased puts	93.25
Weighted average fixed price per Bbl, sold calls	101.94
Enhanced Swap | Derivatives Maturing In 2014 | Crude Oil Derivative
Derivative [Line Items]
Volume of derivative instruments held	840,000
Weighted average fixed price per unit, swaps	98.62
Weighted average fixed price per Bbl, sold puts	80.00
Enhanced Swap | Derivatives maturing in 2015 | Crude Oil Derivative
Derivative [Line Items]
Volume of derivative instruments held	5,578,000
Weighted average fixed price per unit, swaps	93.14
Weighted average fixed price per Bbl, sold puts	80.00
Put Spread Enhanced Swap | Derivatives Maturing In 2014 | Crude Oil Derivative
Derivative [Line Items]
Volume of derivative instruments held	2,480,000
Weighted average fixed price per unit, swaps	93.76
Weighted average fixed price per Bbl, sold puts	80.00
Weighted average fixed price per Bbl, purchased puts	60.00
Put Options Purchased | Derivatives Maturing In 2014 | Crude Oil Derivative
Derivative [Line Items]
Volume of derivative instruments held	840,000
Weighted average fixed price per Bbl, purchased puts	60.00
Basis Protection Swaps | Derivatives Maturing In 2014 | Natural Gas Derivative
Derivative [Line Items]
Volume of derivative instruments held	21,550,000
Weighted average fixed price per unit, swaps	0.24
Basis Protection Swaps | Derivatives maturing in 2015 | Natural Gas Derivative
Derivative [Line Items]
Volume of derivative instruments held	2,400,000
Weighted average fixed price per unit, swaps	0.18