Derivative Financial Instruments Derivative Financial Instruments (Schedule of NGL Derivative Contracts Volume and Weighted Average Prices) (Details)	Mar. 31, 2013
NGL contracts, price per BBL [Member] | Two Thousand Fourteen Collar Contracts With Short Puts [Member]
Derivative [Line Items]
Derivative, Average Cap Price	109.50
Derivative, Average Floor Price	95.00
NGL contracts, price per BBL [Member] | Two Thousand Fourteen Collar Contracts With Short Puts [Member] | Short Put [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Price Per Unit	80.00
NGL contracts, price per BBL [Member] | Two Thousand Thirteen Collar Contracts With Short Puts [Member]
Derivative [Line Items]
Derivative, Average Cap Price	105.28
Derivative, Average Floor Price	89.30
NGL contracts, price per BBL [Member] | Two Thousand Thirteen Collar Contracts With Short Puts [Member] | Short Put [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Price Per Unit	75.20
NGL contract, in BBLS [Member] | Two Thousand Fourteen Collar Contracts With Short Puts [Member]
Derivative [Line Items]
Average Daily NGL Production Derivative Barrels Per Day	1,000
NGL contract, in BBLS [Member] | Two Thousand Thirteen Collar Contracts With Short Puts [Member]
Derivative [Line Items]
Average Daily NGL Production Derivative Barrels Per Day	1,064