Derivative Instruments and Hedging Activities (Details 3) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Derivative Instruments, Gain (Loss) [Line Items]
Amount of (Gain) Loss on Derivative Instruments Recognized in Other Comprehensive (Income) Loss	$ 0	$ (23)	$ 63
Amount of (Gain) Loss on Derivative Instruments Reclassified from Accumulated Other Comprehensive (Income) Loss	1	1	21
Crude Oil
Derivative Instruments, Gain (Loss) [Line Items]
Amount of (Gain) Loss on Derivative Instruments Recognized in Other Comprehensive (Income) Loss	0	0	0
Amount of (Gain) Loss on Derivative Instruments Reclassified from Accumulated Other Comprehensive (Income) Loss	0	0	19	[1]
Natural Gas
Derivative Instruments, Gain (Loss) [Line Items]
Amount of (Gain) Loss on Derivative Instruments Recognized in Other Comprehensive (Income) Loss	0	0	0
Amount of (Gain) Loss on Derivative Instruments Reclassified from Accumulated Other Comprehensive (Income) Loss	0	0	1	[1]
Interest Rate Derivative Instruments in Cash Flow Hedging Relationships
Derivative Instruments, Gain (Loss) [Line Items]
Amount of (Gain) Loss on Derivative Instruments Recognized in Other Comprehensive (Income) Loss	0	(23)	63
Amount of (Gain) Loss on Derivative Instruments Reclassified from Accumulated Other Comprehensive (Income) Loss	$ 1	$ 1	$ 1

[1] Includes effect of commodity derivative instruments previously accounted for as cash flow hedges. All net derivative gains and losses that were deferred in AOCL as a result of previous cash flow hedge accounting, had been reclassified to earnings by December 31, 2010.