Derivative Instruments - Impact on Statements of Income, Fair Value Hedges (Details 2a) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Fair value hedge gains (losses) recorded in income
Derivatives	$ (6,795)	$ 8,000	$ 1,105
Hedged items	5,935	(6,608)	(306)
Total income statement impact	(860)	1,392	799
Hedge ineffectiveness	79	94	175
Excluded components	(939)	1,298	624
Interest Rate Contract [Member]
Fair value hedge gains (losses) recorded in income
Derivatives	(1,238)	532	1,102
Hedged items	1,879	33	(376)
Total income statement impact	641	565	726
Hedge ineffectiveness	(28)	104	175
Excluded components	669	461	551
Foreign exchange
Fair value hedge gains (losses) recorded in income
Derivatives	(3,027)	5,684	1,357
Hedged items	2,925	(3,761)	(1,812)
Total income statement impact	(102)	1,923	(455)
Hedge ineffectiveness	0	0	0
Excluded components	(102)	1,923	(455)
Included revenue related to certain foreign exchange trading derivatives	(3,100)	4,900	278
Commodity
Fair value hedge gains (losses) recorded in income
Derivatives	(2,530)	1,784	(1,354)
Hedged items	1,131	(2,880)	1,882
Total income statement impact	(1,399)	(1,096)	528
Hedge ineffectiveness	107	(10)	0
Excluded components	$ (1,506)	$ (1,086)	$ 528