Derivative Instruments (Details 2) (Crude Oil)	Jun. 30, 2013
ICE Brent | Full 2014 Term | Crude Oil Sales - Three-way collars - Derivative 1
Derivative [Line Items]
Derivative, nonmonetary notional amount	1,000
ICE Brent | Full 2013 Term | Crude Oil Sales - Three-way collars - Derivative 1
Derivative [Line Items]
Derivative, nonmonetary notional amount	1,000
NYMEX WTI | Full 2014 Term | Crude Oil Sales - Three-way collars - Derivative 2
Derivative [Line Items]
Derivative, nonmonetary notional amount	1,000
Put Option | Short | ICE Brent | Full 2014 Term | Crude Oil Sales - Three-way collars - Derivative 1
Derivative [Line Items]
Put (in dollars per MMBtu)	80
Put Option | Short | ICE Brent | Full 2013 Term | Crude Oil Sales - Three-way collars - Derivative 1
Derivative [Line Items]
Put (in dollars per MMBtu)	80
Put Option | Short | NYMEX WTI | Full 2014 Term | Crude Oil Sales - Three-way collars - Derivative 2
Derivative [Line Items]
Put (in dollars per MMBtu)	70
Put Option | Long | ICE Brent | Full 2014 Term | Crude Oil Sales - Three-way collars - Derivative 1
Derivative [Line Items]
Put (in dollars per MMBtu)	100
Put Option | Long | ICE Brent | Full 2013 Term | Crude Oil Sales - Three-way collars - Derivative 1
Derivative [Line Items]
Put (in dollars per MMBtu)	100
Put Option | Long | NYMEX WTI | Full 2014 Term | Crude Oil Sales - Three-way collars - Derivative 2
Derivative [Line Items]
Put (in dollars per MMBtu)	90
Call Option | Short | ICE Brent | Full 2014 Term | Crude Oil Sales - Three-way collars - Derivative 1
Derivative [Line Items]
Call (in dollars per MMBtu)	114.05
Call Option | Short | ICE Brent | Full 2013 Term | Crude Oil Sales - Three-way collars - Derivative 1
Derivative [Line Items]
Call (in dollars per MMBtu)	114.05
Call Option | Short | NYMEX WTI | Full 2014 Term | Crude Oil Sales - Three-way collars - Derivative 2
Derivative [Line Items]
Call (in dollars per MMBtu)	102