Segment Information (Details 3) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Reconciliation from segment income to net income
Total segment income	$ (685)	$ 736	$ 812	$ 2,047
Other operating revenue	4,515	4,571	13,553	13,793
Depreciation and amortization	(1,135)	(1,144)	(3,375)	(3,560)
Impairment of goodwill (Note 2)	1,100	0	1,100	0
Other unassigned operating expenses	(1,047)	(748)	(2,679)	(2,454)
Other income (expense), net	(320)	(314)	(918)	(1,171)
Income tax expense	(40)	(152)	(372)	(332)
Net (loss) income	(1,045)	270	(478)	544
Operating segments
Reconciliation from segment income to net income
Total segment income	2,162	2,243	6,687	6,850
Unallocated amount to segment
Reconciliation from segment income to net income
Other operating revenue	248	257	754	789
Depreciation and amortization	1,135	1,144	3,375	3,560
Impairment of goodwill (Note 2)	(1,100)	0	(1,100)	0
Other unassigned operating expenses	860	620	2,154	2,032
Other income (expense), net	(320)	(314)	(918)	(1,171)
Income tax expense	$ 40	$ 152	$ 372	$ 332