Financial Instruments (Fair value hedges) (Details) (Fair Value Hedges [Member], USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Fair value hedges
Hedge ineffectiveness gain (loss)	$ 14	$ (82)	$ (15)	$ (187)
Hedge amount excluded from assessment of effectiveness	insignificant amounts	insignificant amounts	insignificant amounts	insignificant amounts
Interest Rate Contract [Member]
Fair value hedges
Gain (loss) on derivatives	(2,932)	2,232	(3,841)	785
Gain (loss) on hedged items	2,945	(2,312)	3,826	(962)
Foreign Exchange Contract [Member]
Fair value hedges
Gain (loss) on derivatives	2	(63)	(7)	(111)
Gain (loss) on hedged items	$ (1)	$ 60	$ 7	$ 100