Segment Information (Details 3) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Reconciliation from segment income to net income
Total segment income	$ 657	$ 480	$ 1,311	$ 944
Other operating revenue	4,612	4,406	9,222	6,102
Depreciation and amortization	(1,208)	(1,177)	(2,416)	(1,546)
Other unassigned operating expenses	(835)	(968)	(1,706)	(1,205)
Other income (expense)	(534)	(294)	(857)	(419)
Income tax expense	(49)	(71)	(180)	(199)
Net income	74	115	274	326
Operating segments
Reconciliation from segment income to net income
Total segment income	2,322	2,337	4,688	3,338
Unallocated amount to segment
Reconciliation from segment income to net income
Other operating revenue	266	248	532	379
Depreciation and amortization	(1,208)	(1,177)	(2,416)	(1,546)
Other unassigned operating expenses	(723)	(928)	(1,493)	(1,227)
Other income (expense)	(534)	(294)	(857)	(419)
Income tax expense	$ (49)	$ (71)	$ (180)	$ (199)