Derivatives (Cash Flow Hedges) (Details)	6 Months Ended
	Jun. 30, 2012 bbl
Swap [Member] | WTI - NYMEX [Member] | Crude Oil [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Hedged Volume (in Bbl/day)	1,000
Weighted Average Fixed Price for Swaps	90.20
Swap [Member] | WTI - NYMEX [Member] | Crude Oil [Member] | Start [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Commodity Derivatives Term	Jan'13
Swap [Member] | WTI - NYMEX [Member] | Crude Oil [Member] | End [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Commodity Derivatives Term	Dec'13
Swap [Member] | WTI - NYMEX [Member] | Crude Oil [Member] | Jul'12 - Dec'12 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Hedged Volume (in Bbl/day)	6,250
Weighted Average Fixed Price for Swaps	97.72
Swap [Member] | WTI - NYMEX [Member] | Crude Oil [Member] | Jul'12 - Dec'12 [Member] | Start [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Commodity Derivatives Term	Jul'12
Swap [Member] | WTI - NYMEX [Member] | Crude Oil [Member] | Jul'12 - Dec'12 [Member] | End [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Commodity Derivatives Term	Dec'12
Swap [Member] | WTI - NYMEX [Member] | Crude Oil [Member] | Jan'13 - Dec'13 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Hedged Volume (in Bbl/day)	4,000
Weighted Average Fixed Price for Swaps	102.68
Swap [Member] | WTI - NYMEX [Member] | Crude Oil [Member] | Jan'13 - Dec'13 [Member] | Start [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Commodity Derivatives Term	Jan'13
Swap [Member] | WTI - NYMEX [Member] | Crude Oil [Member] | Jan'13 - Dec'13 [Member] | End [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Commodity Derivatives Term	Dec'13
Swap [Member] | IF - NYMEX (HH) [Member] | Natural Gas [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Hedged Volume (MMBtu/day)	30,000
Weighted Average Fixed Price for Swaps	3.67
Swap [Member] | IF - NYMEX (HH) [Member] | Natural Gas [Member] | Start [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Commodity Derivatives Term	Jan'13
Swap [Member] | IF - NYMEX (HH) [Member] | Natural Gas [Member] | End [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Commodity Derivatives Term	Dec'13
Swap [Member] | IF - NYMEX (HH) [Member] | Natural Gas [Member] | Jul'12 - Dec'12 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Hedged Volume (MMBtu/day)	30,000
Weighted Average Fixed Price for Swaps	5.05
Swap [Member] | IF - NYMEX (HH) [Member] | Natural Gas [Member] | Jul'12 - Dec'12 [Member] | Start [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Commodity Derivatives Term	Jul'12
Swap [Member] | IF - NYMEX (HH) [Member] | Natural Gas [Member] | Jul'12 - Dec'12 [Member] | End [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Commodity Derivatives Term	Dec'12
Swap [Member] | IF - NYMEX (HH) [Member] | Natural Gas [Member] | Jul'12 - Sep'12 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Hedged Volume (MMBtu/day)	20,000
Weighted Average Fixed Price for Swaps	2.98
Swap [Member] | IF - NYMEX (HH) [Member] | Natural Gas [Member] | Jul'12 - Sep'12 [Member] | Start [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Commodity Derivatives Term	Jul'12
Swap [Member] | IF - NYMEX (HH) [Member] | Natural Gas [Member] | Jul'12 - Sep'12 [Member] | End [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Commodity Derivatives Term	Sep'12
Swap [Member] | IF - NYMEX (HH) [Member] | Natural Gas [Member] | Jan'13 - Dec'13 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Hedged Volume (MMBtu/day)	30,000
Weighted Average Fixed Price for Swaps	3.44
Swap [Member] | IF - NYMEX (HH) [Member] | Natural Gas [Member] | Jan'13 - Dec'13 [Member] | Start [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Commodity Derivatives Term	Jan'13
Swap [Member] | IF - NYMEX (HH) [Member] | Natural Gas [Member] | Jan'13 - Dec'13 [Member] | End [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Commodity Derivatives Term	Dec'13
Swap [Member] | IF - PEPL [Member] | Natural Gas [Member] | Jul'12 - Dec'12 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Hedged Volume (MMBtu/day)	15,000
Weighted Average Fixed Price for Swaps	5.62
Swap [Member] | IF - PEPL [Member] | Natural Gas [Member] | Jul'12 - Dec'12 [Member] | Start [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Commodity Derivatives Term	Jul'12
Swap [Member] | IF - PEPL [Member] | Natural Gas [Member] | Jul'12 - Dec'12 [Member] | End [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Commodity Derivatives Term	Dec'12
Swap [Member] | OPIS - Conway [Member] | Liquids [Member] | Jul'12 - Dec'12 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Hedged Volume (Gal/mo)	180,006	[1]
Weighted Average Fixed Price for Swaps	2.11	[1]
Swap [Member] | OPIS - Conway [Member] | Liquids [Member] | Jul'12 - Dec'12 [Member] | Start [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Commodity Derivatives Term	Jul'12	[1]
Swap [Member] | OPIS - Conway [Member] | Liquids [Member] | Jul'12 - Dec'12 [Member] | End [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Commodity Derivatives Term	Dec'12	[1]
Swap [Member] | OPIS - Mont Belvieu [Member] | Liquids [Member] | Jul'12 - Dec'12 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Hedged Volume (Gal/mo)	310,000	[2]
Weighted Average Fixed Price for Swaps	0.69	[2]
Swap [Member] | OPIS - Mont Belvieu [Member] | Liquids [Member] | Jul'12 - Dec'12 [Member] | Start [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Commodity Derivatives Term	Jul'12	[2]
Swap [Member] | OPIS - Mont Belvieu [Member] | Liquids [Member] | Jul'12 - Dec'12 [Member] | End [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Commodity Derivatives Term	Dec'12	[2]
Collar [Member] | IF - NYMEX (HH) [Member] | Natural Gas [Member] | Jan'13 - Dec'13 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Hedged Volume (MMBtu/day)	20,000
Collar [Member] | IF - NYMEX (HH) [Member] | Natural Gas [Member] | Jan'13 - Dec'13 [Member] | Start [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Commodity Derivatives Term	Jan'13
Weighted Average Fixed Price for Swaps	3.25
Collar [Member] | IF - NYMEX (HH) [Member] | Natural Gas [Member] | Jan'13 - Dec'13 [Member] | End [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Commodity Derivatives Term	Dec'13
Weighted Average Fixed Price for Swaps	3.75

[1] Types of liquids involved are natural gasoline.

[2] Types of liquids involved are ethane.