Derivative Instruments and Hedging Activities (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013
Derivative Instruments and Hedging Activities [Abstract]
AOCL amount, net of tax, to be reclassified to interest expense over the life of the debt	$ 25
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months	$ 2
Crude Oil Commodity Contract | Swaps - NYMEX WTI 2013
Derivative [Line Items]
Period	2013
Index	NYMEX WTI  (1)	[1]
Volume Per Day	9,000
Weighted Average Fixed Price	90.16
Put Option Premium	0.00
Weighted Average Short Put Price
Weighted Average Floor Price
Weighted Average Ceiling Price
Crude Oil Commodity Contract | Swaps - Dated Brent 2013
Derivative [Line Items]
Period	2013
Index	Dated Brent
Volume Per Day	3,000
Weighted Average Fixed Price	98.03
Put Option Premium	0.00
Weighted Average Short Put Price
Weighted Average Floor Price
Weighted Average Ceiling Price
Crude Oil Commodity Contract | Two Way Collar - NYMEX WTI 2013
Derivative [Line Items]
Period	2013
Index	NYMEX WTI	[1]
Volume Per Day	5,000
Weighted Average Fixed Price
Put Option Premium	0.00
Weighted Average Short Put Price
Weighted Average Floor Price	95.00
Weighted Average Ceiling Price	115.00
Crude Oil Commodity Contract | Three Way Collars - NYMEX WTI 2013
Derivative [Line Items]
Period	2013
Index	NYMEX WTI	[1]
Volume Per Day	7,000
Weighted Average Fixed Price
Put Option Premium	0.00
Weighted Average Short Put Price	63.57
Weighted Average Floor Price	83.57
Weighted Average Ceiling Price	109.04
Crude Oil Commodity Contract | Three Way Collars - Dated Brent 2013
Derivative [Line Items]
Period	2013
Index	Dated Brent
Volume Per Day	13,000
Weighted Average Fixed Price
Put Option Premium	0.00
Weighted Average Short Put Price	81.15
Weighted Average Floor Price	100.75
Weighted Average Ceiling Price	124.68
Crude Oil Commodity Contract | Put Option - NYMEX WTI 2013
Derivative [Line Items]
Period	2013
Index	NYMEX WTI	[2]
Volume Per Day	11,000
Weighted Average Fixed Price
Put Option Premium	5.97
Weighted Average Short Put Price
Weighted Average Floor Price	97.60
Weighted Average Ceiling Price
Crude Oil Commodity Contract | Swaps - NYMEX WTI 2014
Derivative [Line Items]
Period	2014
Index	NYMEX WTI	[1]
Volume Per Day	32,000
Weighted Average Fixed Price	92.62
Put Option Premium	0.00
Weighted Average Short Put Price
Weighted Average Floor Price
Weighted Average Ceiling Price
Crude Oil Commodity Contract | Swaps - Dated Brent 2014
Derivative [Line Items]
Period	2014
Index	Dated Brent
Volume Per Day	10,000
Weighted Average Fixed Price	103.33
Put Option Premium	0.00
Weighted Average Short Put Price
Weighted Average Floor Price
Weighted Average Ceiling Price
Crude Oil Commodity Contract | Three Way Collars - NYMEX WTI 2014
Derivative [Line Items]
Period	2014
Index	NYMEX WTI	[1]
Volume Per Day	9,000
Weighted Average Fixed Price
Put Option Premium	0.00
Weighted Average Short Put Price	75.89
Weighted Average Floor Price	90.89
Weighted Average Ceiling Price	100.44
Crude Oil Commodity Contract | Three Way Collars - Dated Brent 2014
Derivative [Line Items]
Period	2014
Index	Dated Brent
Volume Per Day	5,000
Weighted Average Fixed Price	0.00
Put Option Premium	0.00
Weighted Average Short Put Price	84.00
Weighted Average Floor Price	97.20
Weighted Average Ceiling Price	129.70
Crude Oil Commodity Contract | Swaps - NYMEX WTI 2015
Derivative [Line Items]
Period	2015
Index	NYMEX WTI	[1]
Volume Per Day	5,000
Weighted Average Fixed Price	88.02
Put Option Premium	0.00
Weighted Average Short Put Price
Weighted Average Floor Price
Weighted Average Ceiling Price
Crude Oil Commodity Contract | Swaps - Dated Brent 2015
Derivative [Line Items]
Period	2015
Index	Dated Brent
Volume Per Day	5,000
Weighted Average Fixed Price	99.04
Put Option Premium	0.00
Weighted Average Short Put Price
Weighted Average Floor Price
Weighted Average Ceiling Price
Crude Oil Commodity Contract | Three Way Collars - NYMEX WTI 2015
Derivative [Line Items]
Period	2015
Index	NYMEX WTI	[1]
Volume Per Day	10,000
Weighted Average Fixed Price
Put Option Premium	0.00
Weighted Average Short Put Price	68.50
Weighted Average Floor Price	88.50
Weighted Average Ceiling Price	92.87
Crude Oil Commodity Contract | Three Way Collars - Dated Brent 2015
Derivative [Line Items]
Period	2015
Index	Dated Brent
Volume Per Day	5,000
Weighted Average Fixed Price
Put Option Premium	0.00
Weighted Average Short Put Price	75.00
Weighted Average Floor Price	95.00
Weighted Average Ceiling Price	112.53
Natural Gas Commodity Contract | Swaps - NYMEX HH 2013
Derivative [Line Items]
Period	2013
Index	NYMEX HH (1)	[3]
Volume Per Day	60,000
Weighted Average Fixed Price	4.58
Weighted Average Short Put Price
Weighted Average Floor Price
Weighted Average Ceiling Price
Natural Gas Commodity Contract | Two Way Collar - NYMEX HH 2013
Derivative [Line Items]
Period	2013
Index	NYMEX HH	[3]
Volume Per Day	40,000
Weighted Average Fixed Price
Weighted Average Short Put Price
Weighted Average Floor Price	3.25
Weighted Average Ceiling Price	5.14
Natural Gas Commodity Contract | Three Way Collars - NYMEX HH 2013
Derivative [Line Items]
Period	2013
Index	NYMEX HH	[3]
Volume Per Day	100,000
Weighted Average Fixed Price
Weighted Average Short Put Price	3.88
Weighted Average Floor Price	4.75
Weighted Average Ceiling Price	5.63
Natural Gas Commodity Contract | Swaps - NYMEX HH 2014
Derivative [Line Items]
Period	2014
Index	NYMEX HH	[3]
Volume Per Day	60,000
Weighted Average Fixed Price	4.24
Weighted Average Short Put Price
Weighted Average Floor Price
Weighted Average Ceiling Price
Natural Gas Commodity Contract | Three Way Collar - NYMEX HH 2014
Derivative [Line Items]
Period	2014
Index	NYMEX HH	[3]
Volume Per Day	160,000
Weighted Average Fixed Price
Weighted Average Short Put Price	2.64
Weighted Average Floor Price	3.64
Weighted Average Ceiling Price	5.02
Natural Gas Commodity Contract | Swaps - NYMEX HH 2015
Derivative [Line Items]
Period	2015
Index	NYMEX HH	[3]
Volume Per Day	30,000
Weighted Average Fixed Price	4.25
Weighted Average Short Put Price
Weighted Average Floor Price
Weighted Average Ceiling Price
Natural Gas Commodity Contract | Three Way Collars - NYMEX HH 2015
Derivative [Line Items]
Period	2015
Index	NYMEX HH	[3]
Volume Per Day	100,000
Weighted Average Fixed Price
Weighted Average Short Put Price	3.50
Weighted Average Floor Price	4.25
Weighted Average Ceiling Price	5.01

[1] West Texas Intermediate

[2] For put options, we typically pay a premium to the counterparty in exchange for the sale of the instrument. If the index price is below the floor price of the put option, we receive the difference between the floor price and the index price multiplied by the contract volumes less the option premium. If the index price settles at or above the floor price of the put option, we pay only the option premium.

[3] Henry Hub