Derivative Financial Instruments and Hedging Activities - Income (Losses) Recognized in Income (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Derivatives, Fair Value [Line Items]
Interest expense	$ 788	$ 952	$ 1,623	$ 1,899
Operating expenses	345	377	703	747
AOCI Attributable to Parent [Member]
Derivatives, Fair Value [Line Items]
Gains (Losses) Recognized In Accumulated Other Comprehensive Loss	23	(30)	(207)	(93)
(Gains) Losses Reclassified From Accumulated Other Comprehensive Income	(57)	12	56	60
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	(7)	(9)	(12)	(20)
(Gains) Losses Reclassified From Accumulated Other Comprehensive Income	5	11	13	22
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	39	(19)	(180)	(71)
(Gains) Losses Reclassified From Accumulated Other Comprehensive Income	(63)	2	41	41
Cash Flow Hedging [Member] \| Unrealized (Loss) Gain on Hedges [Member] \| Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Gains (Losses) Recognized In Accumulated Other Comprehensive Loss	(9)	(2)	(15)	(2)
(Gains) Losses Reclassified From Accumulated Other Comprehensive Income	1	(1)	2	(3)
Interest Expense [Member]
Derivatives, Fair Value [Line Items]
Total	(52)	(68)	(114)	(133)
Operating Expense [Member]
Derivatives, Fair Value [Line Items]
Total	115	20	10	(12)
Designated as Hedging Instrument [Member] \| Foreign Currency Translation Adjustment [Member]
Derivatives, Fair Value [Line Items]
Gain (loss) to be reclassified in next twelve months			(88)
Designated as Hedging Instrument [Member] \| Interest Expense [Member] \| Fair Value Hedging [Member] \| Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Hedged items	(66)	(313)	(569)	(523)
Interest rate swaps and Foreign currency swaps	(56)	285	375	466
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	(9)	(15)	(21)	(31)
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	(2)	1	(3)	4
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	(28)	(21)	(57)	(39)
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	(41)	(25)	(1)	7
Interest rate swaps and Foreign currency swaps	43	27	4	(4)
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	113	18	7	(15)
Not Designated as Hedging Instrument [Member] \| Interest Expense [Member]
Derivatives, Fair Value [Line Items]
Interest rate contracts	109	(5)	161	(10)
Not Designated as Hedging Instrument [Member] \| Operating Expense [Member]
Derivatives, Fair Value [Line Items]
Interest rate contracts	$ 0	$ 0	$ 0	$ 0

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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