Investment Securities - Available-for-Sale and Held-to-Maturity (Detail) - USD ($) $ in Millions		Jun. 30, 2023		Dec. 31, 2022
Debt Securities Available For Sale And Held To Maturity [Line Items]
Held-to-maturity securities, Amortized Cost		$ 86,938	[1]	$ 88,740
Held-to-maturity securities, Unrealized Gains		0		3
Held-to-maturity securities, Unrealized Losses		(10,653)		(10,869)
Held-to-maturity securities, Fair Value		76,285	[1]	77,874
Available-for-sale Securities, Amortized Cost		76,888		81,450
Available-for-sale securities, Unrealized Gains		15		26
Available-for-sale securities, Unrealized Losses		(7,682)		(8,566)
Available-for-sale securities, Fair Value	[3]	69,221	[1],[2]	72,910
U.S. Treasury and Agencies [Member]
Debt Securities Available For Sale And Held To Maturity [Line Items]
Held-to-maturity securities, Amortized Cost		1,345		1,344
Held-to-maturity securities, Unrealized Losses		(58)		(51)
Held-to-maturity securities, Fair Value		1,287		1,293
Available-for-sale Securities, Amortized Cost		21,328		24,801
Available-for-sale securities, Unrealized Gains		1		1
Available-for-sale securities, Unrealized Losses		(2,361)		(2,769)
Available-for-sale securities, Fair Value		18,968		22,033
Residential Mortgage-Backed Securities [Member] | Agency [Member]
Debt Securities Available For Sale And Held To Maturity [Line Items]
Held-to-maturity securities, Amortized Cost		83,898		85,693
Held-to-maturity securities, Unrealized Gains		0		2
Held-to-maturity securities, Unrealized Losses		(10,578)		(10,810)
Held-to-maturity securities, Fair Value		73,320		74,885
Available-for-sale Securities, Amortized Cost		28,253		32,060
Available-for-sale securities, Unrealized Gains		3		8
Available-for-sale securities, Unrealized Losses		(2,595)		(2,797)
Available-for-sale securities, Fair Value		25,661		29,271
Commercial [Member] | Agency [Member]
Debt Securities Available For Sale And Held To Maturity [Line Items]
Held-to-maturity securities, Amortized Cost		1,695		1,703
Held-to-maturity securities, Unrealized Gains		0		1
Held-to-maturity securities, Unrealized Losses		(17)		(8)
Held-to-maturity securities, Fair Value		1,678		1,696
Available-for-sale Securities, Amortized Cost		8,719		8,736
Available-for-sale securities, Unrealized Losses		(1,532)		(1,591)
Available-for-sale securities, Fair Value		7,187		7,145
Commercial [Member] | Non Agency Securities [Member]
Debt Securities Available For Sale And Held To Maturity [Line Items]
Available-for-sale Securities, Amortized Cost		7		7
Available-for-sale securities, Unrealized Losses		(1)
Available-for-sale securities, Fair Value		6		7
Asset-Backed Securities [Member]
Debt Securities Available For Sale And Held To Maturity [Line Items]
Available-for-sale Securities, Amortized Cost		7,487	[4]	4,356
Available-for-sale securities, Unrealized Gains		5		5
Available-for-sale securities, Unrealized Losses		(41)		(38)
Available-for-sale securities, Fair Value		7,451	[4]	4,323
Obligations of State and Political Subdivisions [Member]
Debt Securities Available For Sale And Held To Maturity [Line Items]
Available-for-sale Securities, Amortized Cost		11,091	[5],[6]	11,484
Available-for-sale securities, Unrealized Gains		6		12
Available-for-sale securities, Unrealized Losses		(1,153)		(1,371)
Available-for-sale securities, Fair Value		9,944	[5],[6]	10,125
Other [Member]
Debt Securities Available For Sale And Held To Maturity [Line Items]
Available-for-sale Securities, Amortized Cost		4		6
Available-for-sale securities, Fair Value		4		6
Excluding Portfolio Level Basis Adjustments [Member]
Debt Securities Available For Sale And Held To Maturity [Line Items]
Available-for-sale Securities, Amortized Cost		76,889	[1],[2]	81,450
Available-for-sale securities, Unrealized Gains		15		26
Available-for-sale securities, Unrealized Losses		(7,683)		(8,566)
Available-for-sale securities, Fair Value		69,221		72,910
Portfolio Level Basis Adjustments [Member]
Debt Securities Available For Sale And Held To Maturity [Line Items]
Available-for-sale Securities, Amortized Cost	[7]	(1)		0
Available-for-sale securities, Unrealized Gains	[7]	0		0
Available-for-sale securities, Unrealized Losses	[7]	1		0
Available-for-sale securities, Fair Value	[7]	$ 0		$ 0

[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.

[2] Amortized cost excludes portfolio level basis adjustments of $(1) million.

[3] Includes only collateral pledged by the Company where counterparties have the right to sell or pledge the collateral.

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

[5] 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.

[6] 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.

[7] Represents fair value hedge basis adjustments related to active portfolio layer method hedges of available-for-sale investment securities, which are not allocated to individual securities in the portfolio. For additional information, refer to Note 13.