Derivatives and Hedging Activities - Gain (Loss) from Interest Rate Hedges and Related Hedged Borrowings and Deposits (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Derivative [Line Items]
Interest expense	$ 1,310	$ 2,090	$ 2,882	$ 5,527
Interest Rate Contract [Member] \| Fair Value Hedging [Member] \| Derivative Contracts Accounted for as Hedges [Member]
Derivative [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Income, Net	1,475	353	(3,930)	6,939
Gain (Loss) Recognized On Hedged Borrowings and Deposits	$ (1,559)	$ (564)	$ 3,626	$ (7,243)

Amount of the increase (decrease) in fair value of the hedged item in a fair value hedge recognized in the income statement.

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Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

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

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