Risk Management And Hedging Activities (Schedule Of Net Long Or Short Positions Expected To Be Realized) (Detail)	9 Months Ended
	Sep. 30, 2012 bbl	Sep. 30, 2011 bbl
Crude Oil [Member]
Derivative [Line Items]
2011		(87,058)
2012	(170,759)	(904,171)
2013	(927,310)	(947,249)
2014	(547,500)	(547,500)
2015	(365,000)	(365,000)
2016	(183,000)	(183,000)
Natural Gas [Member]
Derivative [Line Items]
2011		3,278,700
2012	(240,000)	(22,686,000)
2013	(6,865,000)	1,635,000
2014	(365,000)	(365,000)
Natural Gas Liquids [Member]
Derivative [Line Items]
2011		(379,887)
2012	(788,429)	(145,082)
2013	(700,975)
2014	(629,625)
2015	(155,250)
Natural Gas Basis Swaps [Member]
Derivative [Line Items]
2011		2,477,500
2012	605,000	13,800,000
2013	10,072,500	1,800,000
2014	(900,000)