Derivative Instruments and Hedging Activities - Part 2 (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Assets
Derivative Assets, Gross	$ 188	$ 100
Liabilities
Derivative Liabilities, Gross	506	657
Subject to netting arrangement [Member]
Assets
Derivative Assets, Gross	82	25
Derivative Assets Not Offset Under Netting Arrangements	(16)	(9)
Derivative Assets Not Offset By Collateral	0	0
Derivative Assets, Net	66	16
Liabilities
Derivative Liabilities, Gross	392	522
Derivative Liabilities Not Offset Under Netting Arrangements	(16)	(9)
Derivative Liabilities Not Offset By Collateral	(5)	(5)
Derivative Liabilities, Net	371	508
Current [Member]
Assets
Derivative Assets, Gross	50	14
Liabilities
Derivative Liabilities, Gross	182	186
Noncurrent [Member]
Assets
Derivative Assets, Gross	138	86
Liabilities
Derivative Liabilities, Gross	324	471
Designated as Hedging Instruments [Member]
Assets
Derivative Assets, Gross	8	60
Liabilities
Derivative Liabilities, Gross	407	565
Not Designated as Hedging Instruments [Member]
Assets
Derivative Assets, Gross	128	92
Liabilities
Derivative Liabilities, Gross	99	92
No longer carried at fair value [Member]
Assets
Derivative Assets, Gross	177	186
Liabilities
Derivative Liabilities, Gross	190	191
Interest rate derivatives [Member]
Assets
Derivative Assets, Gross	40	2
Liabilities
Derivative Liabilities, Gross	389	565
Interest rate derivatives [Member] | Designated as Hedging Instruments [Member]
Assets
Derivative Assets, Gross	38	0
Liabilities
Derivative Liabilities, Gross	374	544
Interest rate derivatives [Member] | Not Designated as Hedging Instruments [Member]
Assets
Derivative Assets, Gross	2	2
Liabilities
Derivative Liabilities, Gross	15	21
Cross currency derivatives [Member]
Assets
Derivative Assets, Gross	5	6
Liabilities
Derivative Liabilities, Gross	8	6
Cross currency derivatives [Member] | Designated as Hedging Instruments [Member]
Assets
Derivative Assets, Gross	5	6
Liabilities
Derivative Liabilities, Gross	8	6
Cross currency derivatives [Member] | Not Designated as Hedging Instruments [Member]
Assets
Derivative Assets, Gross	0	0
Liabilities
Derivative Liabilities, Gross	0	0
Foreign currency derivatives [Member]
Assets
Derivative Assets, Gross	104	81
Liabilities
Derivative Liabilities, Gross	24	14
Foreign currency derivatives [Member] | Designated as Hedging Instruments [Member]
Assets
Derivative Assets, Gross	10	0
Liabilities
Derivative Liabilities, Gross	15	7
Foreign currency derivatives [Member] | Not Designated as Hedging Instruments [Member]
Assets
Derivative Assets, Gross	94	81
Liabilities
Derivative Liabilities, Gross	9	7
Commodity derivatives [Member]
Assets
Derivative Assets, Gross	39	11
Liabilities
Derivative Liabilities, Gross	85	72
Commodity derivatives [Member] | Designated as Hedging Instruments [Member]
Assets
Derivative Assets, Gross	7	2
Liabilities
Derivative Liabilities, Gross	10	8
Commodity derivatives [Member] | Not Designated as Hedging Instruments [Member]
Assets
Derivative Assets, Gross	32	9
Liabilities
Derivative Liabilities, Gross	$ 75	$ 64