Derivatives and Hedging Activities - Gain (Loss) from Interest Rate Hedges and Related Hedged Borrowings and Deposits (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Derivative [Line Items]
Interest expense	$ 1,848	$ 4,451	$ 7,375	$ 13,519
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	(1,111)	2,465	5,829	6,054
Gain (Loss) Recognized On Hedged Borrowings and Deposits	$ 916	$ (2,548)	$ (6,327)	$ (6,366)

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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