Investment Securities - Available-for-Sale and Held-to-Maturity (Detail) - USD ($) $ in Millions	Mar. 31, 2022		Dec. 31, 2021
Debt Securities Available For Sale And Held To Maturity [Line Items]
Held-to-maturity securities, Amortized Cost	$ 43,654	[1]	$ 41,858
Held-to-maturity securities, Unrealized Gains			2
Held-to-maturity securities, Unrealized Losses	(3,082)		(48)
Held-to-maturity securities, Fair Value	40,572	[1]	41,812
Available-for-sale Securities, Amortized Cost	129,642	[1]	132,241
Available-for-sale securities, Unrealized Gains	249		1,534
Available-for-sale securities, Unrealized Losses	(6,298)		(812)
Available-for-sale securities, Fair Value	123,593	[1]	132,963
U.S. Treasury and Agencies [Member]
Debt Securities Available For Sale And Held To Maturity [Line Items]
Available-for-sale Securities, Amortized Cost	27,653		36,648
Available-for-sale securities, Unrealized Gains	28		205
Available-for-sale securities, Unrealized Losses	(1,331)		(244)
Available-for-sale securities, Fair Value	26,350		36,609
Residential Mortgage-Backed Securities [Member] | Agency [Member]
Debt Securities Available For Sale And Held To Maturity [Line Items]
Held-to-maturity securities, Amortized Cost	43,654		41,858
Held-to-maturity securities, Unrealized Gains			2
Held-to-maturity securities, Unrealized Losses	(3,082)		(48)
Held-to-maturity securities, Fair Value	40,572		41,812
Available-for-sale Securities, Amortized Cost	82,508		76,761
Available-for-sale securities, Unrealized Gains	70		665
Available-for-sale securities, Unrealized Losses	(3,586)		(347)
Available-for-sale securities, Fair Value	78,992		77,079
Commercial [Member] | Agency [Member]
Debt Securities Available For Sale And Held To Maturity [Line Items]
Available-for-sale Securities, Amortized Cost	8,769		8,633
Available-for-sale securities, Unrealized Gains			53
Available-for-sale securities, Unrealized Losses	(806)		(201)
Available-for-sale securities, Fair Value	7,963		8,485
Asset-Backed Securities [Member]
Debt Securities Available For Sale And Held To Maturity [Line Items]
Available-for-sale Securities, Amortized Cost	4	[2]	62
Available-for-sale securities, Unrealized Gains	3		4
Available-for-sale securities, Fair Value	7	[2]	66
Obligations of State and Political Subdivisions [Member]
Debt Securities Available For Sale And Held To Maturity [Line Items]
Available-for-sale Securities, Amortized Cost	10,701	[3],[4]	10,130
Available-for-sale securities, Unrealized Gains	148		607
Available-for-sale securities, Unrealized Losses	(575)		(20)
Available-for-sale securities, Fair Value	10,274	[3],[4]	10,717
Other [Member]
Debt Securities Available For Sale And Held To Maturity [Line Items]
Available-for-sale Securities, Amortized Cost	7		7
Available-for-sale securities, Fair Value	$ 7		$ 7

[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.

[2] Information related to asset and mortgage-backed securities included above is presented based upon weighted-average maturities that take into account anticipated future prepayments.

[3] Information related to obligations of state and political subdivisions is presented based upon yield to first optional call date if the security is purchased at a premium, and yield to maturity if the security is purchased at par or a discount.

[4] Maturity calculations for obligations of state and political subdivisions are based on the first optional call date for securities with a fair value above par and the contractual maturity date for securities with a fair value equal to or below par.