Derivative Financial Instruments and Hedging Activities (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Derivative [Line Items]
Debt Carrying Value Fair Value	$ 36,300		$ 37,500
Income Effect of Derivative Financial Instruments [Abstract]
Derivative, Gain (Loss) on Derivative, Net	(24)	$ (183)
Balance Sheet Effect of Derivative Financial Instruments [Abstract]
Fair Value of Derivative Assets	639		1,065
Fair Value of Derivative Liabilities	1,337		512
Derivative, Notional Amount	83,939		85,778
Derivative, Collateral, Obligation to Return Cash	102		26
Derivative, Collateral, Right to Reclaim Cash	109		71
Derivative Asset, Not Offset, Policy Election Deduction	189		415
Derivative Liability, Not Offset, Policy Election Deduction	189		415
Interest Rate Contract [Member] \| Designated as Hedging Instrument [Member] \| Fair Value Hedging [Member]
Income Effect of Derivative Financial Instruments [Abstract]
Net interest settlements and accruals excluded from the assessment of hedge effectiveness	76	101
Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments	(986)	(641)
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge	991	590
Balance Sheet Effect of Derivative Financial Instruments [Abstract]
Derivative, Notional Amount	21,985		23,893
Interest Rate Contract [Member] \| Designated as Hedging Instrument [Member] \| Currency Swap
Income Effect of Derivative Financial Instruments [Abstract]
Net interest settlements and accruals excluded from the assessment of hedge effectiveness	(3)	(3)
Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments	(37)	(50)
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge	41	44
Balance Sheet Effect of Derivative Financial Instruments [Abstract]
Derivative, Notional Amount	885		885
Interest Rate Contract [Member] \| Designated as Hedging Instrument [Member] \| Level 2 [Member] \| Fair Value, Recurring [Member] \| Fair Value Hedging [Member]
Balance Sheet Effect of Derivative Financial Instruments [Abstract]
Fair Value of Derivative Assets	41		544
Fair Value of Derivative Liabilities	758		274
Interest Rate Contract [Member] \| Designated as Hedging Instrument [Member] \| Level 2 [Member] \| Fair Value, Recurring [Member] \| Currency Swap
Balance Sheet Effect of Derivative Financial Instruments [Abstract]
Fair Value of Derivative Assets	0		0
Fair Value of Derivative Liabilities	79		49
Interest Rate Contract [Member] \| Not Designated as Hedging Instrument [Member]
Income Effect of Derivative Financial Instruments [Abstract]
Derivative, Gain (Loss) on Derivative, Net	123	(31)
Balance Sheet Effect of Derivative Financial Instruments [Abstract]
Derivative, Notional Amount	49,854		50,060
Interest Rate Contract [Member] \| Not Designated as Hedging Instrument [Member] \| Level 2 [Member] \| Fair Value, Recurring [Member]
Balance Sheet Effect of Derivative Financial Instruments [Abstract]
Fair Value of Derivative Assets	496		338
Fair Value of Derivative Liabilities	195		126
Foreign Exchange Contract [Member] \| Not Designated as Hedging Instrument [Member]
Income Effect of Derivative Financial Instruments [Abstract]
Derivative, Gain (Loss) on Derivative, Net	(2)	52
Balance Sheet Effect of Derivative Financial Instruments [Abstract]
Derivative, Notional Amount	4,695		4,407
Foreign Exchange Contract [Member] \| Not Designated as Hedging Instrument [Member] \| Level 2 [Member] \| Fair Value, Recurring [Member]
Balance Sheet Effect of Derivative Financial Instruments [Abstract]
Fair Value of Derivative Assets	51		66
Fair Value of Derivative Liabilities	29		2
Cross Currency Interest Rate Contract [Member] \| Not Designated as Hedging Instrument [Member]
Income Effect of Derivative Financial Instruments [Abstract]
Derivative, Gain (Loss) on Derivative, Net	(227)	$ (245)
Balance Sheet Effect of Derivative Financial Instruments [Abstract]
Derivative, Notional Amount	6,520		6,533
Cross Currency Interest Rate Contract [Member] \| Not Designated as Hedging Instrument [Member] \| Level 2 [Member] \| Fair Value, Recurring [Member]
Balance Sheet Effect of Derivative Financial Instruments [Abstract]
Fair Value of Derivative Assets	51		117
Fair Value of Derivative Liabilities	$ 276		$ 61

Balance Sheet Effect of Derivative Financial Instruments [Abstract]

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Income Effect of Derivative Financial Instruments [Abstract]

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