Derivative Financial Instruments and Hedging Activities - Income (Losses) Recognized in Income (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Derivatives, Fair Value [Line Items]
Interest expense	$ 952	$ 803	$ 1,899	$ 1,535
Operating expenses	377	382	747	747
AOCI Attributable to Parent [Member]
Derivatives, Fair Value [Line Items]
Gains (Losses) Recognized In Accumulated Other Comprehensive Loss			(93)	(35)
(Gains) Losses Reclassified From Accumulated Other Comprehensive Income	12	74	60	53
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	(9)	0	(20)	0
(Gains) Losses Reclassified From Accumulated Other Comprehensive Income	11	0	22	0
Cash Flow Hedging [Member]
Derivatives, Fair Value [Line Items]
Gains (Losses) Recognized In Accumulated Other Comprehensive Loss	(30)	(57)
Cash Flow Hedging [Member] \| Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Gains (Losses) Recognized In Accumulated Other Comprehensive Loss	(2)	1
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	(19)	(58)	(71)	(40)
(Gains) Losses Reclassified From Accumulated Other Comprehensive Income	2	74	41	56
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			(2)	5
(Gains) Losses Reclassified From Accumulated Other Comprehensive Income	(1)	0	(3)	(3)
Interest Expense [Member]
Derivatives, Fair Value [Line Items]
Total	(68)	(31)	(133)	(39)
Operating Expense [Member]
Derivatives, Fair Value [Line Items]
Total	20	(201)	(12)	(155)
Designated as Hedging Instrument [Member] \| Foreign Currency Translation Adjustment [Member]
Derivatives, Fair Value [Line Items]
Gain (loss) to be reclassified in next twelve months			14
Designated as Hedging Instrument [Member] \| Interest Expense [Member] \| Fair Value Hedging [Member] \| Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Hedged items	(313)	69	(523)	277
Interest rate swaps and Foreign currency swaps	285	(76)	466	(286)
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	(31)	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	3	4	7
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	(21)	(13)	(39)	(22)
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	(25)	0	7	0
Interest rate swaps and Foreign currency swaps	27	0	(4)	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	18	(92)	(15)	(68)
Not Designated as Hedging Instrument [Member] \| Interest Expense [Member]
Derivatives, Fair Value [Line Items]
Interest rate contracts	(5)	(1)	(10)	5
Foreign currency swaps	0	(13)	0	(20)
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	$ (109)	$ 0	$ (87)

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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