Financial Instruments (Cash flow hedges) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended															12 Months Ended	3 Months Ended	12 Months Ended
	Mar. 31, 2014 Cash Flow Hedge [Member]	Mar. 31, 2013 Cash Flow Hedge [Member]	Mar. 31, 2014 Cash Flow Hedge [Member] Interest Rate Contract [Member]	Mar. 31, 2013 Cash Flow Hedge [Member] Interest Rate Contract [Member]	Mar. 31, 2014 Cash Flow Hedge [Member] Foreign Exchange Contract [Member]	Mar. 31, 2013 Cash Flow Hedge [Member] Foreign Exchange Contract [Member]	Mar. 31, 2014 Cash Flow Hedge [Member] Commodity Contract [Member]	Mar. 31, 2013 Cash Flow Hedge [Member] Commodity Contract [Member]	Mar. 31, 2014 Net Investment Hedge [Member]	Mar. 31, 2013 Net Investment Hedge [Member]	Mar. 31, 2014 Net Investment Hedge [Member] Foreign Exchange Contract [Member]	Mar. 31, 2013 Net Investment Hedge [Member] Foreign Exchange Contract [Member]	Mar. 31, 2014 Fair Value Hedges [Member]	Mar. 31, 2013 Fair Value Hedges [Member]	Mar. 31, 2014 Fair Value Hedges [Member] Interest Rate Contract [Member]	Dec. 31, 2013 Fair Value Hedges [Member] Interest Rate Contract [Member]	Mar. 31, 2014 Fair Value Hedges [Member] Foreign Exchange Contract [Member]	Dec. 31, 2013 Fair Value Hedges [Member] Foreign Exchange Contract [Member]
Summary Of Cash Flow Hedge Activity [Line Items]
Gain (loss) recognized in AOCI	$ 157	$ (8)	$ 3	$ (11)	$ 156	$ 4	$ (2)	$ (1)			$ (1,033)	$ 2,105
Gain (loss) reclassified from AOCI into earnings	37	(131)	(69)	(102)	108	(28)	(2)	(1)			10	(124)
Pre-tax gain (loss) included in AOCI related to cash flow hedges of forecasted transactions	(118)
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months	160
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
Maximum term of hedged forecasted transactions	19	20
Hedge ineffectiveness gain (loss)									$ (142)	$ (166)			$ (16)	$ (34)	$ (1,005)	$ 881	$ (3)	$ 8