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, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Financial Assets
Cash and due from banks	$ 18,115	$ 21,453	$ 19,246	$ 19,505
Investment securities held-to-maturity	46,285	46,050
Loans	283,709	282,837
Financial Liabilities
Long-term debt	40,680	41,340
Carrying Amount [Member]
Financial Assets
Cash and due from banks	18,115	21,453
Federal funds sold and securities purchased under resale agreements	3,868	306
Investment securities held-to-maturity	46,285	46,050
Loans held for sale	35	21
Loans	283,709	282,837
Other	2,065	2,412
Financial Liabilities
Time deposits	47,051	44,554
Short-term borrowings	13,924	12,921
Long-term debt	40,680	41,340
Other	3,463	1,726
Fair Value [Member]
Financial Assets
Cash and due from banks	18,115	21,453
Federal funds sold and securities purchased under resale agreements	3,868	306
Investment securities held-to-maturity	45,735	44,964
Loans held for sale	35	21
Loans	286,873	284,790
Other	2,065	2,412
Financial Liabilities
Time deposits	46,912	44,140
Short-term borrowings	13,691	12,678
Long-term debt	40,705	41,003
Other	3,463	1,726
Fair Value [Member] \| Level 1 [Member]
Financial Assets
Cash and due from banks	18,115	21,453
Investment securities held-to-maturity	4,495	4,594
Fair Value [Member] \| Level 2 [Member]
Financial Assets
Federal funds sold and securities purchased under resale agreements	3,868	306
Investment securities held-to-maturity	41,228	40,359
Other	1,008	1,241
Financial Liabilities
Time deposits	46,912	44,140
Short-term borrowings	13,691	12,678
Long-term debt	40,705	41,003
Other	1,396
Fair Value [Member] \| Level 3 [Member]
Financial Assets
Investment securities held-to-maturity	12	11
Loans held for sale	35	21
Loans	286,873	284,790
Other	1,057	1,171
Financial Liabilities
Other	$ 2,067	$ 1,726