Derivative Instruments (Details 2) (Crude Oil)	Mar. 31, 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
ICE Brent | Sold Put | Full 2014 Term | Crude Oil Sales - Three-way collars - Derivative 1
Derivative [Line Items]
Put (in dollars per MMBtu)	80
ICE Brent | Sold Put | Full 2013 Term | Crude Oil Sales - Three-way collars - Derivative 1
Derivative [Line Items]
Put (in dollars per MMBtu)	80
ICE Brent | Put Options Purchased | Full 2014 Term | Crude Oil Sales - Three-way collars - Derivative 1
Derivative [Line Items]
Put (in dollars per MMBtu)	100
ICE Brent | Put Options Purchased | Full 2013 Term | Crude Oil Sales - Three-way collars - Derivative 1
Derivative [Line Items]
Put (in dollars per MMBtu)	100
ICE Brent | Sold Call | Full 2014 Term | Crude Oil Sales - Three-way collars - Derivative 1
Derivative [Line Items]
Call (in dollars per MMBtu)	114.05
ICE Brent | Sold Call | Full 2013 Term | Crude Oil Sales - Three-way collars - Derivative 1
Derivative [Line Items]
Call (in dollars per MMBtu)	114.05
NYMEX WTI | Full 2014 Term | Crude Oil Sales - Three-way collars - Derivative 2
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	1,000
NYMEX WTI | Sold Put | Full 2014 Term | Crude Oil Sales - Three-way collars - Derivative 2
Derivative [Line Items]
Put (in dollars per MMBtu)	70
NYMEX WTI | Put Options Purchased | Full 2014 Term | Crude Oil Sales - Three-way collars - Derivative 2
Derivative [Line Items]
Put (in dollars per MMBtu)	90
NYMEX WTI | Sold Call | Full 2014 Term | Crude Oil Sales - Three-way collars - Derivative 2
Derivative [Line Items]
Call (in dollars per MMBtu)	102