Derivative Activities (Notional Volumes Of Commodity Derivative Contracts) (Details)	Feb. 28, 2013	Dec. 31, 2012
Oil Positions [Member] | 2013 [Member] | WTI [Member] | Swaps [Member]
Derivative [Line Items]
Hedged volume per day		7,170
Average price		98.74
Oil Positions [Member] | 2013 [Member] | LLS [Member] | Swaps [Member]
Derivative [Line Items]
Hedged volume per day		1,400
Average price		99.51
Oil Positions [Member] | 2014 [Member] | WTI [Member] | Swaps [Member]
Derivative [Line Items]
Hedged volume per day	464	6,661
Average price	93.50	96.35
Oil Positions [Member] | 2014 [Member] | WTI [Member] | Collars [Member]
Derivative [Line Items]
Hedged volume per day		425
Average floor price		90.00
Average ceiling price		106.50
Oil Positions [Member] | 2014 [Member] | LLS [Member] | Swaps [Member]
Derivative [Line Items]
Hedged volume per day		1,900
Average price		98.77
Oil Positions [Member] | 2015 [Member] | WTI [Member] | Swaps [Member]
Derivative [Line Items]
Hedged volume per day		6,721
Average price		94.52
Oil Positions [Member] | 2015 [Member] | WTI [Member] | Collars [Member]
Derivative [Line Items]
Hedged volume per day		1,025
Average floor price		90.00
Average ceiling price		110.00
Oil Positions [Member] | 2016 [Member] | WTI [Member] | Swaps [Member]
Derivative [Line Items]
Hedged volume per day		5,698
Average price		90.81
Oil Positions [Member] | 2016 [Member] | WTI [Member] | Collars [Member]
Derivative [Line Items]
Hedged volume per day		1,500
Average floor price		80.00
Average ceiling price		102.00
Oil Positions [Member] | 2017 [Member] | WTI [Member] | Swaps [Member]
Derivative [Line Items]
Hedged volume per day		4,997
Average price		86.88
Natural Gas Position [Member] | 2013 [Member] | Henry Hub [Member] | Swaps [Member]
Derivative [Line Items]
Hedged volume per day		30,441
Average price		6.01
Natural Gas Position [Member] | 2013 [Member] | Henry Hub [Member] | Basis Swap [Member]
Derivative [Line Items]
Hedged volume per day		18,466
Average price		(0.17)
Natural Gas Position [Member] | 2013 [Member] | Henry Hub [Member] | Collars [Member]
Derivative [Line Items]
Hedged volume per day		2,466
Average floor price		6.50
Average ceiling price		8.65
Natural Gas Position [Member] | 2014 [Member] | Henry Hub [Member] | Swaps [Member]
Derivative [Line Items]
Hedged volume per day		26,622
Average price		6.18
Natural Gas Position [Member] | 2014 [Member] | Henry Hub [Member] | Basis Swap [Member]
Derivative [Line Items]
Hedged volume per day		17,066
Average price		(0.19)
Natural Gas Position [Member] | 2014 [Member] | Henry Hub [Member] | Collars [Member]
Derivative [Line Items]
Hedged volume per day		4,966
Average floor price		5.74
Average ceiling price		7.51
Natural Gas Position [Member] | 2015 [Member] | Put [Member]
Derivative [Line Items]
Hedged volume per day		420
Average price		4.00
Natural Gas Position [Member] | 2015 [Member] | Henry Hub [Member] | Swaps [Member]
Derivative [Line Items]
Hedged volume per day		7,191
Average price		5.34
Natural Gas Position [Member] | 2015 [Member] | Henry Hub [Member] | Basis Swap [Member]
Derivative [Line Items]
Hedged volume per day		14,400
Average price		(0.19)
Natural Gas Position [Member] | 2015 [Member] | Henry Hub [Member] | Collars [Member]
Derivative [Line Items]
Hedged volume per day		18,000
Average floor price		5.00
Average ceiling price		7.48
Natural Gas Position [Member] | 2016 [Member] | Put [Member]
Derivative [Line Items]
Hedged volume per day		11,350
Average price		4.00
Natural Gas Position [Member] | 2016 [Member] | Henry Hub [Member] | Swaps [Member]
Derivative [Line Items]
Hedged volume per day		11,350
Average price		4.27
Natural Gas Position [Member] | 2016 [Member] | Henry Hub [Member] | Collars [Member]
Derivative [Line Items]
Hedged volume per day		630
Average floor price		4.00
Average ceiling price		5.55
Natural Gas Position [Member] | 2017 [Member] | Put [Member]
Derivative [Line Items]
Hedged volume per day		10,445
Average price		4.00
Natural Gas Position [Member] | 2017 [Member] | Henry Hub [Member] | Swaps [Member]
Derivative [Line Items]
Hedged volume per day		10,445
Average price		4.47
Natural Gas Position [Member] | 2017 [Member] | Henry Hub [Member] | Collars [Member]
Derivative [Line Items]
Hedged volume per day		595
Average floor price		4.00
Average ceiling price		6.15