Fair Values of Assets and Liabilities - Estimated Fair Values of Financial Instruments (Detail) - USD ($) $ in Millions	Mar. 31, 2023		Dec. 31, 2022
Financial Assets
Cash and due from banks	$ 67,228		$ 53,542
Investment securities held-to-maturity	88,462	[1]	88,740
Loans	380,846		381,277
Financial Liabilities
Long-term debt	42,045		39,829
Carrying Amount [Member]
Financial Assets
Cash and due from banks	67,228		53,542
Federal funds sold and securities purchased under resale agreements	1,698		356
Investment securities held-to-maturity	88,462		88,740
Loans held for sale	391		351
Loans	380,846		381,277
Other	3,894		2,962
Financial Liabilities
Time deposits	37,515		32,946
Short-term borrowings	54,818		29,527
Long-term debt	42,045		39,829
Other	5,351		5,137
Fair Value [Member]
Financial Assets
Cash and due from banks	67,228		53,542
Federal funds sold and securities purchased under resale agreements	1,698		356
Investment securities held-to-maturity	78,876		77,874
Loans held for sale	391		351
Loans	372,857		368,874
Other	3,894		2,962
Financial Liabilities
Time deposits	37,264		32,338
Short-term borrowings	54,418		29,145
Long-term debt	39,960		37,622
Other	5,351		5,137
Fair Value [Member] | Level 1 [Member]
Financial Assets
Cash and due from banks	67,228		53,542
Federal funds sold and securities purchased under resale agreements	0		0
Investment securities held-to-maturity	1,307		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	1,698		356
Investment securities held-to-maturity	77,569		76,581
Loans held for sale	0		0
Loans	0		0
Other	3,143		2,224
Financial Liabilities
Time deposits	37,264		32,338
Short-term borrowings	54,418		29,145
Long-term debt	39,960		37,622
Other	1,461		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	391		351
Loans	372,857		368,874
Other	751		738
Financial Liabilities
Time deposits	0		0
Short-term borrowings	0		0
Long-term debt	0		0
Other	$ 3,890		$ 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.