Segment Information (Details 3) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Reconciliation from segment income to net income
Total segment income	$ 736	$ 548	$ 2,047	$ 1,492
Other operating revenue	4,571	4,596	13,793	10,698
Depreciation and amortization	(1,144)	(1,228)	(3,560)	(2,774)
Other unassigned operating expenses	(748)	(870)	(2,454)	(2,075)
Other income (expense)	(314)	(317)	(1,171)	(736)
Income tax expense	(152)	(93)	(332)	(292)
Net income	270	138	544	464
Operating segments
Reconciliation from segment income to net income
Total segment income	2,277	2,306	6,965	5,644
Unallocated amount to segment
Reconciliation from segment income to net income
Other operating revenue	257	247	789	626
Depreciation and amortization	(1,144)	(1,228)	(3,560)	(2,774)
Other unassigned operating expenses	(654)	(777)	(2,147)	(2,004)
Other income (expense)	(314)	(317)	(1,171)	(736)
Income tax expense	$ (152)	$ (93)	$ (332)	$ (292)