Fair Values of Assets and Liabilities - Estimated Fair Values of Financial Instruments (Detail) - USD ($) $ in Millions	Jun. 30, 2023		Dec. 31, 2022
Financial Assets
Cash and due from banks	$ 70,642		$ 53,542
Investment securities held-to-maturity	86,938	[1]	88,740
Loans	372,264		381,277
Financial Liabilities
Long-term debt	45,283		39,829
Carrying Amount [Member]
Financial Assets
Cash and due from banks	70,642		53,542
Federal funds sold and securities purchased under resale agreements	1,606		356
Investment securities held-to-maturity	86,938		88,740
Loans held for sale	81		351
Loans	372,264		381,277
Other	3,158		2,962
Financial Liabilities
Time deposits	51,969		32,946
Short-term borrowings	30,389		29,527
Long-term debt	45,283		39,829
Other	5,238		5,137
Fair Value [Member]
Financial Assets
Cash and due from banks	70,642		53,542
Federal funds sold and securities purchased under resale agreements	1,606		356
Investment securities held-to-maturity	76,285		77,874
Loans held for sale	81		351
Loans	364,104		368,874
Other	3,158		2,962
Financial Liabilities
Time deposits	51,664		32,338
Short-term borrowings	30,077		29,145
Long-term debt	43,007		37,622
Other	5,238		5,137
Fair Value [Member] | Level 1 [Member]
Financial Assets
Cash and due from banks	70,642		53,542
Federal funds sold and securities purchased under resale agreements	0		0
Investment securities held-to-maturity	1,287		1,293
Loans held for sale	0		0
Loans	0		0
Other	0		0
Financial Liabilities
Time deposits	0		0
Short-term borrowings	0		0
Long-term debt	0		0
Other	0		0
Fair Value [Member] | Level 2 [Member]
Financial Assets
Cash and due from banks	0		0
Federal funds sold and securities purchased under resale agreements	1,606		356
Investment securities held-to-maturity	74,998		76,581
Loans held for sale	0		0
Loans	0		0
Other	2,459		2,224
Financial Liabilities
Time deposits	51,664		32,338
Short-term borrowings	30,077		29,145
Long-term debt	43,007		37,622
Other	1,416		1,500
Fair Value [Member] | Level 3 [Member]
Financial Assets
Cash and due from banks	0		0
Federal funds sold and securities purchased under resale agreements	0		0
Investment securities held-to-maturity	0		0
Loans held for sale	81		351
Loans	364,104		368,874
Other	699		738
Financial Liabilities
Time deposits	0		0
Short-term borrowings	0		0
Long-term debt	0		0
Other	$ 3,822		$ 3,637

[1] The weighted-average maturity of total held-to-maturity investment securities was 9.2 years at December 31, 2022, with a corresponding weighted-average yield of 2.18 percent. The weighted-average maturity of total available-for-sale investment securities was 7.4 years at December 31, 2022, with a corresponding weighted-average yield of 2.94 percent.