Supplemental Information (Derivatives and Hedging - Cash Flow Hedges) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Summary Of Cash Flow Hedge Activity [Line Items]
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months			$ 86
Maximum term of hedged forecasted transactions			16 years	17 years
Cash Flow Hedges [Member]
Summary Of Cash Flow Hedge Activity [Line Items]
Gain (loss) recognized in AOCI	$ 2	$ (124)	$ (43)	$ (761)
Gain (loss) reclassified from AOCI into earnings	(57)	(109)	(128)	(691)
Pre-tax gain (loss) included in AOCI related to cash flow hedges of forecasted transactions			1
Interest Rate Contracts
Summary Of Cash Flow Hedge Activity [Line Items]
Gain (loss) recognized in AOCI	1	10	32	0
Gain (loss) reclassified from AOCI into earnings	(12)	(39)	(67)	(100)
Currency Exchange Contracts
Summary Of Cash Flow Hedge Activity [Line Items]
Gain (loss) recognized in AOCI	0	(132)	(76)	(757)
Gain (loss) reclassified from AOCI into earnings	(46)	(69)	(59)	(589)
Commodity Contracts
Summary Of Cash Flow Hedge Activity [Line Items]
Gain (loss) recognized in AOCI	1	(2)	1	(4)
Gain (loss) reclassified from AOCI into earnings	$ 0	$ (1)	$ (3)	$ (2)