For banks and other depository institutions: Includes cash on hand (currency and coin), cash items in process of collection, noninterest bearing deposits due from other financial institutions (including corporate credit unions), and noninterest bearing balances with the Federal Reserve Banks, Federal Home Loan Banks and central banks.

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Fair Values of Assets and Liabilities - Estimated Fair Values of Financial Instruments (Detail) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Financial Assets
Cash and due from banks	$ 43,501	$ 62,580	$ 46,805	$ 22,405
Loans	288,084	290,393
Financial Liabilities
Long-term debt	37,419	41,297
Carrying Amount [Member]
Financial Assets
Cash and due from banks	43,501	62,580
Federal funds sold and securities purchased under resale agreements	403	377
Loans held for sale	122	237
Loans	288,084	290,393
Other	1,877	1,772
Financial Liabilities
Time deposits	23,711	30,694
Short-term borrowings	10,009	10,009
Long-term debt	37,419	41,297
Other	3,905	4,052
Fair Value [Member]
Financial Assets
Cash and due from banks	43,501	62,580
Federal funds sold and securities purchased under resale agreements	403	377
Loans held for sale	122	237
Loans	296,703	300,419
Other	1,877	1,772
Financial Liabilities
Time deposits	23,834	30,864
Short-term borrowings	9,963	9,956
Long-term debt	38,086	42,485
Other	3,905	4,052
Fair Value [Member] \| Level 1 [Member]
Financial Assets
Cash and due from banks	43,501	62,580
Fair Value [Member] \| Level 2 [Member]
Financial Assets
Federal funds sold and securities purchased under resale agreements	403	377
Other	899	731
Financial Liabilities
Time deposits	23,834	30,864
Short-term borrowings	9,963	9,956
Long-term debt	38,086	42,485
Other	1,175	1,234
Fair Value [Member] \| Level 3 [Member]
Financial Assets
Loans held for sale	122	237
Loans	296,703	300,419
Other	978	1,041
Financial Liabilities
Other	$ 2,730	$ 2,818