Financial Instruments (Fair value hedges) (Details) (Fair Value Hedges [Member], USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Fair value hedges
Hedge ineffectiveness gain (loss)	$ (49)	$ 14	$ (65)	$ (15)
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	725	(2,932)	1,715	(3,841)
Gain (loss) on hedged items	(774)	2,945	(1,779)	3,826
Foreign Exchange Contract [Member]
Fair value hedges
Gain (loss) on derivatives	(5)	2	(3)	(7)
Gain (loss) on hedged items	$ 5	$ (1)	$ (2)	$ 7