Segment Information (Details 3) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Reconciliation from segment income to net income
Total segment income	$ 654	$ 464
Other operating revenue	4,610	1,696
Depreciation and amortization	(1,208)	(369)
Other unassigned operating expenses	(871)	(237)
Other income (expense)	(323)	(125)
Income tax expense	(131)	(128)
Net income	200	211
Operating segments
Reconciliation from segment income to net income
Total segment income	2,354	983
Other operating revenue	266	131
Depreciation and amortization	(1,208)	(369)
Other unassigned operating expenses	(758)	(281)
Other income (expense)	(323)	(125)
Income tax expense	(131)	(128)
Net income	$ 200	$ 211