Financial Instruments (Fair value hedges) (Details) (Fair Value Hedges [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Fair value hedges
Hedge ineffectiveness gain (loss)	$ (16)	$ (29)
Hedge amount excluded from assessment of effectiveness	insignificant amounts	insignificant amounts
Interest Rate Contract [Member]
Fair value hedges
Gain (loss) on derivatives	990	(909)
Gain (loss) on hedged items	(1,005)	881
Foreign Exchange Contract [Member]
Fair value hedges
Gain (loss) on derivatives	2	(9)
Gain (loss) on hedged items	$ 3	$ 8