Derivative Financial Instruments and Hedging Activities - Income (Losses) Recognized in Income (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Derivatives, Fair Value [Line Items]
Interest expense	$ 879	$ 838	$ 2,778	$ 2,373
Operating expenses	384	369	1,131	1,116
AOCI Attributable to Parent [Member]
Derivatives, Fair Value [Line Items]
Gains (Losses) Recognized In Accumulated Other Comprehensive Loss	(140)	(10)	(233)	(45)
(Gains) Losses Reclassified From Accumulated Other Comprehensive Income	128	11	188	64
Fair Value Hedging [Member] \| Foreign Currency Translation Adjustment [Member] \| Foreign Currency Swaps [Member]
Derivatives, Fair Value [Line Items]
Gains (Losses) Recognized In Accumulated Other Comprehensive Loss	(10)	0	(30)	0
(Gains) Losses Reclassified From Accumulated Other Comprehensive Income	10	0	32	0
Cash Flow Hedging [Member] \| Foreign Currency Translation Adjustment [Member] \| Foreign Currency Swaps [Member]
Derivatives, Fair Value [Line Items]
Gains (Losses) Recognized In Accumulated Other Comprehensive Loss	(127)	(10)	(198)	(50)
(Gains) Losses Reclassified From Accumulated Other Comprehensive Income	119	13	160	69
Cash Flow Hedging [Member] \| Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member] \| Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Gains (Losses) Recognized In Accumulated Other Comprehensive Loss	(3)	0	(5)	5
(Gains) Losses Reclassified From Accumulated Other Comprehensive Income	(1)	(2)	(4)	(5)
Interest Expense [Member]
Derivatives, Fair Value [Line Items]
Total	(27)	(37)	(160)	(76)
Operating Expense [Member]
Derivatives, Fair Value [Line Items]
Total	(133)	(28)	(145)	(183)
Designated as Hedging Instrument [Member] \| Foreign Currency Translation Adjustment [Member]
Derivatives, Fair Value [Line Items]
Gain (loss) to be reclassified in next twelve months			(17)
Designated as Hedging Instrument [Member] \| Interest Expense [Member] \| Fair Value Hedging [Member] \| Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Hedged items	(159)	68	(682)	345
Interest rate swaps and Foreign currency swaps	80	(73)	546	(359)
Designated as Hedging Instrument [Member] \| Interest Expense [Member] \| Fair Value Hedging [Member] \| Foreign Currency Swaps [Member]
Derivatives, Fair Value [Line Items]
Hedged items	0	0	0	0
Interest rate swaps and Foreign currency swaps	(15)	0	(46)	0
Designated as Hedging Instrument [Member] \| Interest Expense [Member] \| Cash Flow Hedging [Member] \| Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Interest rate swaps and Foreign currency swaps	1	4	5	11
Designated as Hedging Instrument [Member] \| Interest Expense [Member] \| Cash Flow Hedging [Member] \| Foreign Currency Swaps [Member]
Derivatives, Fair Value [Line Items]
Interest rate swaps and Foreign currency swaps	(23)	(14)	(62)	(36)
Designated as Hedging Instrument [Member] \| Operating Expense [Member] \| Fair Value Hedging [Member] \| Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Hedged items	0	0	0	0
Interest rate swaps and Foreign currency swaps	0	0	0	0
Designated as Hedging Instrument [Member] \| Operating Expense [Member] \| Fair Value Hedging [Member] \| Foreign Currency Swaps [Member]
Derivatives, Fair Value [Line Items]
Hedged items	78	0	85	0
Interest rate swaps and Foreign currency swaps	(77)	0	(81)	0
Designated as Hedging Instrument [Member] \| Operating Expense [Member] \| Cash Flow Hedging [Member] \| Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Interest rate swaps and Foreign currency swaps	0	0	0	0
Designated as Hedging Instrument [Member] \| Operating Expense [Member] \| Cash Flow Hedging [Member] \| Foreign Currency Swaps [Member]
Derivatives, Fair Value [Line Items]
Interest rate swaps and Foreign currency swaps	(134)	(23)	(149)	(91)
Not Designated as Hedging Instrument [Member] \| Interest Expense [Member]
Derivatives, Fair Value [Line Items]
Interest rate contracts	89	(7)	79	(2)
Foreign currency swaps	0	(15)	0	(35)
Not Designated as Hedging Instrument [Member] \| Operating Expense [Member]
Derivatives, Fair Value [Line Items]
Interest rate contracts	0	0	0	0
Foreign currency swaps	$ 0	$ (5)	$ 0	$ (92)

The estimated net amount of existing gains or losses on cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months.

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Amount of gain (loss) from the increase (decrease) in fair value of derivative and nonderivative instruments designated as fair value hedging instruments recognized in the income statement.

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Amount of realized and unrealized gain (loss) of derivative instruments not designated or qualifying as hedging instruments.

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Amount of gain (loss) recognized in earnings in the period from the increase (decrease) in fair value of foreign currency derivatives not designated as hedging instruments.

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Amount of gain (loss) included in earnings for the period from the increase (decrease) in fair value of interest rate derivatives not designated as hedging instruments.

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Amount of the cost of borrowed funds accounted for as interest expense.

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