Financial Instruments (Cash flow hedges) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Cash Flow Hedge [Member]
Summary Of Cash Flow Hedge Activity [Line Items]
Gain (loss) recognized in AOCI	$ 1	$ 254	$ 248	$ 515
Gain (loss) reclassified from AOCI into earnings	(21)	136	(96)	224
Pre-tax gain (loss) included in AOCI related to cash flow hedges of forecasted transactions			(413)
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months			294
Gain Loss Related To Hedge Forecasted Transactions And Firm Commitments That Did Not Occur By End Of Originally Specified Period	insignificant gains and losses	insignificant gains and losses	insignificant gains and losses	insignificant gains and losses
Maximum term of hedged forecasted transactions			19	20
Hedge ineffectiveness gain (loss)	0	1	1	4
Cash Flow Hedge [Member] | Interest Rate Contract [Member]
Summary Of Cash Flow Hedge Activity [Line Items]
Gain (loss) recognized in AOCI	(24)	(68)	(15)	(147)
Gain (loss) reclassified from AOCI into earnings	(88)	(116)	(282)	(380)
Cash Flow Hedge [Member] | Foreign Exchange Contract [Member]
Summary Of Cash Flow Hedge Activity [Line Items]
Gain (loss) recognized in AOCI	25	322	263	662
Gain (loss) reclassified from AOCI into earnings	67	252	186	604
Net Investment Hedge [Member]
Summary Of Cash Flow Hedge Activity [Line Items]
Hedge ineffectiveness gain (loss)	(161)	(183)	(514)	(663)
Net Investment Hedge [Member] | Foreign Exchange Contract [Member]
Summary Of Cash Flow Hedge Activity [Line Items]
Gain (loss) recognized in AOCI	645	(2,939)	3,162	(2,588)
Gain (loss) reclassified from AOCI into earnings	(169)	39	(278)	27
Fair Value Hedges [Member]
Summary Of Cash Flow Hedge Activity [Line Items]
Hedge ineffectiveness gain (loss)	$ (40)	$ (113)	$ (55)	$ (300)