Fair Values of Assets and Liabilities - Estimated Fair Values of Financial Instruments (Detail) - USD ($) $ in Millions	Jun. 30, 2022		Dec. 31, 2021
Financial Assets
Cash and due from banks	$ 39,124		$ 28,905
Investment securities held-to-maturity	61,503	[1]	41,858
Loans	326,537		306,304
Financial Liabilities
Long-term debt	29,408		32,125
Carrying Amount [Member]
Financial Assets
Cash and due from banks	39,124		28,905
Federal funds sold and securities purchased under resale agreements	520		359
Investment securities held-to-maturity	61,503		41,858
Loans held for sale	1,170		1,152
Loans	326,537		306,304
Other	2,391		1,521
Financial Liabilities
Time deposits	30,622		22,665
Short-term borrowings	23,128		9,750
Long-term debt	29,408		32,125
Other	3,896		3,862
Fair Value [Member]
Financial Assets
Cash and due from banks	39,124		28,905
Federal funds sold and securities purchased under resale agreements	520		359
Investment securities held-to-maturity	55,657		41,812
Loans held for sale	1,170		1,152
Loans	321,095		312,724
Other	2,391		1,521
Financial Liabilities
Time deposits	30,039		22,644
Short-term borrowings	22,789		9,646
Long-term debt	27,901		32,547
Other	3,896		3,862
Fair Value [Member] | Level 1 [Member]
Financial Assets
Cash and due from banks	39,124		28,905
Investment securities held-to-maturity	1,337
Fair Value [Member] | Level 2 [Member]
Financial Assets
Federal funds sold and securities purchased under resale agreements	520		359
Investment securities held-to-maturity	54,320		41,812
Other	1,679		630
Financial Liabilities
Time deposits	30,039		22,644
Short-term borrowings	22,789		9,646
Long-term debt	27,901		32,547
Other	1,135		1,170
Fair Value [Member] | Level 3 [Member]
Financial Assets
Loans held for sale	1,170		1,152
Loans	321,095		312,724
Other	712		891
Financial Liabilities
Other	$ 2,761		$ 2,692

[1] The weighted-average maturity of total held-to-maturity investment securities was 7.4 years at December 31, 2021, with a corresponding weighted-average yield of 1.45 percent. The weighted-average maturity of total available-for-sale investment securities was 5.5 years at December 31, 2021, with a corresponding weighted-average yield of 1.73 percent.