Derivative Financial Instruments (Narrative) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	May 08, 2013 NGL contract, in BBLS [Member] May through December Two Thousand Thirteen Collar Contracts [Member] bbl	May 08, 2013 NGL contract, in BBLS [Member] July through December Two Thousand Thirteen Collar Contracts [Member] bbl	May 08, 2013 NGL contract, in BBLS [Member] Two Thousand Fourteen Collar Contracts [Member] bbl	May 08, 2013 NGL contracts, price per BBL [Member] May through December Two Thousand Thirteen Collar Contracts [Member]	May 08, 2013 NGL contracts, price per BBL [Member] July through December Two Thousand Thirteen Collar Contracts [Member]	May 08, 2013 NGL contracts, price per BBL [Member] Two Thousand Fourteen Collar Contracts [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Average Daily NGL Production Derivative Barrels Per Day		2,000	500	3,000
Derivative, Average Cap Price					12.60	13.02	13.72
Derivative, Average Floor Price					10.50	10.50	10.78
Derivative, Fixed Interest Rate	3.21%
Notional amount of debt	$ 250