Investment Securities - Amortized Cost, Fair Value and Yield by Maturity Date (Detail) - USD ($) $ in Millions		6 Months Ended		12 Months Ended
		Jun. 30, 2023		Dec. 31, 2022
Contractual Maturities of Investment Securities [Line Items]
Available-for-sale securities, Amortized Cost		$ 76,888		$ 81,450
Available-for-sale securities, total, fair value	[2]	$ 69,221	[1],[3]	$ 72,910
Available-for-sale securities, total, weighted-average maturity in years		6 years 9 months 18 days	[1],[3]	7 years 4 months 24 days
Available-for-sale securities, total, weighted-average yield		3.09%	[1],[3],[4]	2.94%
Held-to-maturity securities, Amortized Cost		$ 86,938	[3]	$ 88,740
Held-to-maturity securities, total, fair value		$ 76,285	[3]	$ 77,874
Held-to-maturity securities, total, weighted-average maturity in years	[3]	9 years 1 month 6 days
Held-to-maturity securities, total, weighted-average yield		2.21%	[3],[4]	2.18%
U.S. Treasury and Agencies [Member]
Contractual Maturities of Investment Securities [Line Items]
Available-for-sale securities, maturing in one year or less, amortized cost		$ 13
Available-for-sale securities, maturing after one year through five years, amortized cost		6,140
Available-for-sale securities, maturing after five years through ten years, amortized cost		12,981
Available-for-sale securities, maturing after ten years, amortized cost		2,194
Available-for-sale securities, Amortized Cost		21,328		$ 24,801
Available-for-sale securities, maturing in one year or less, fair value		13
Available-for-sale securities, maturing after one year through five years, fair value		5,809
Available-for-sale securities, maturing after five years through ten years, fair value		11,462
Available-for-sale securities, maturing after ten years, fair value		1,684
Available-for-sale securities, total, fair value		$ 18,968		22,033
Available-for-sale securities, maturing in one year or less, weighted-average maturity in years		2 months 12 days
Available-for-sale securities, maturing after one year through five years, weighted-average maturity in years		3 years 8 months 12 days
Available-for-sale securities, maturing after five years through ten years, weighted-average maturity in years		6 years 9 months 18 days
Available-for-sale securities, maturing after ten years, weighted- average maturity in years		11 years 1 month 6 days
Available-for-sale securities, total, weighted-average maturity in years		6 years 4 months 24 days
Available-for-sale securities, maturing in one year or less, weighted-average yield	[4]	4.72%
Available-for-sale securities, maturing after one year through five years, weighted-average yield	[4]	2.79%
Available-for-sale securities, maturing after five years through ten years, weighted-average yield	[4]	2.20%
Available-for-sale securities, maturing after ten years, weighted-average yield	[4]	2.00%
Available-for-sale securities, total, weighted-average yield	[4]	2.35%
Held-to-maturity securities, maturing in one year or less, amortized cost		$ 50
Held-to-maturity securities, maturing after one year through five years, amortized cost		1,295
Held-to-maturity securities, Amortized Cost		1,345		1,344
Held-to-maturity securities, maturing in one year or less, fair value		49
Held-to-maturity securities, maturing after one year through five years, fair value		1,238
Held-to-maturity securities, total, fair value		$ 1,287		1,293
Held-to-maturity securities, maturing in one year or less, weighted-average maturity in years		9 months 18 days
Held-to-maturity securities, maturing after one year through five years, weighted-average maturity in years		2 years 10 months 24 days
Held-to-maturity securities, total, weighted-average maturity in years		2 years 9 months 18 days
Held-to-maturity securities, maturing in one year or less, weighted-average yield	[4]	2.67%
Held-to-maturity securities, maturing after one year through five years, weighted-average yield	[4]	2.85%
Held-to-maturity securities, total, weighted-average yield	[4]	2.85%
Mortgage-Backed Securities [Member]
Contractual Maturities of Investment Securities [Line Items]
Available-for-sale securities, maturing in one year or less, amortized cost	[5]	$ 134
Available-for-sale securities, maturing after one year through five years, amortized cost	[5]	8,980
Available-for-sale securities, maturing after five years through ten years, amortized cost	[5]	26,491
Available-for-sale securities, maturing after ten years, amortized cost	[5]	1,374
Available-for-sale securities, Amortized Cost	[5]	36,979
Available-for-sale securities, maturing in one year or less, fair value	[5]	130
Available-for-sale securities, maturing after one year through five years, fair value	[5]	8,325
Available-for-sale securities, maturing after five years through ten years, fair value	[5]	23,211
Available-for-sale securities, maturing after ten years, fair value	[5]	1,188
Available-for-sale securities, total, fair value	[5]	$ 32,854
Available-for-sale securities, maturing in one year or less, weighted-average maturity in years	[5]	10 months 24 days
Available-for-sale securities, maturing after one year through five years, weighted-average maturity in years	[5]	3 years 1 month 6 days
Available-for-sale securities, maturing after five years through ten years, weighted-average maturity in years	[5]	7 years 7 months 6 days
Available-for-sale securities, maturing after ten years, weighted- average maturity in years	[5]	11 years 1 month 6 days
Available-for-sale securities, total, weighted-average maturity in years	[5]	6 years 7 months 6 days
Available-for-sale securities, maturing in one year or less, weighted-average yield	[4],[5]	2.45%
Available-for-sale securities, maturing after one year through five years, weighted-average yield	[4],[5]	2.42%
Available-for-sale securities, maturing after five years through ten years, weighted-average yield	[4],[5]	3.02%
Available-for-sale securities, maturing after ten years, weighted-average yield	[4],[5]	3.65%
Available-for-sale securities, total, weighted-average yield	[4],[5]	2.90%
Held-to-maturity securities, maturing in one year or less, amortized cost	[5]	$ 22
Held-to-maturity securities, maturing after one year through five years, amortized cost	[5]	1,436
Held-to-maturity securities, maturing after five years through ten years, amortized cost	[5]	70,260
Held-to-maturity securities, maturing after ten years, amortized cost	[5]	13,875
Held-to-maturity securities, Amortized Cost	[5]	85,593
Held-to-maturity securities, maturing in one year or less, fair value	[5]	22
Held-to-maturity securities, maturing after one year through five years, fair value	[5]	1,419
Held-to-maturity securities, maturing after five years through ten years, fair value	[5]	61,972
Held-to-maturity securities, maturing after ten years, fair value	[5]	11,585
Held-to-maturity securities, total, fair value	[5]	$ 74,998
Held-to-maturity securities, maturing in one year or less, weighted-average maturity in years	[5]	9 months 18 days
Held-to-maturity securities, maturing after one year through five years, weighted-average maturity in years	[5]	2 years 7 months 6 days
Held-to-maturity securities, maturing after five years through ten years, weighted-average maturity in years	[5]	9 years 2 months 12 days
Held-to-maturity securities, maturing after ten years, weighted-average maturity in years	[5]	10 years 2 months 12 days
Held-to-maturity securities, total, weighted-average maturity in years	[5]	9 years 2 months 12 days
Held-to-maturity securities, maturing in one year or less, weighted-average yield	[4],[5]	4.95%
Held-to-maturity securities, maturing after one year through five years, weighted-average yield	[4],[5]	4.60%
Held-to-maturity securities, maturing after five years through ten years, weighted-average yield	[4],[5]	2.18%
Held-to-maturity securities, maturing after ten years, weighted-average yield	[4],[5]	2.05%
Held-to-maturity securities, total, weighted-average yield	[4],[5]	2.20%
Asset-Backed Securities [Member]
Contractual Maturities of Investment Securities [Line Items]
Available-for-sale securities, maturing in one year or less, amortized cost	[5]	$ 1
Available-for-sale securities, maturing after one year through five years, amortized cost	[5]	7,104
Available-for-sale securities, maturing after five years through ten years, amortized cost	[5]	382
Available-for-sale securities, Amortized Cost		7,487	[5]	4,356
Available-for-sale securities, maturing in one year or less, fair value	[5]	1
Available-for-sale securities, maturing after one year through five years, fair value	[5]	7,068
Available-for-sale securities, maturing after five years through ten years, fair value	[5]	382
Available-for-sale securities, total, fair value		$ 7,451	[5]	4,323
Available-for-sale securities, maturing in one year or less, weighted-average maturity in years	[5]	3 months 18 days
Available-for-sale securities, maturing after one year through five years, weighted-average maturity in years	[5]	1 year 7 months 6 days
Available-for-sale securities, maturing after five years through ten years, weighted-average maturity in years	[5]	5 years 7 months 6 days
Available-for-sale securities, total, weighted-average maturity in years	[5]	1 year 9 months 18 days
Available-for-sale securities, maturing in one year or less, weighted-average yield	[4],[5]	7.57%
Available-for-sale securities, maturing after one year through five years, weighted-average yield	[4],[5]	5.02%
Available-for-sale securities, maturing after five years through ten years, weighted-average yield	[4],[5]	6.96%
Available-for-sale securities, total, weighted-average yield	[4],[5]	5.12%
Obligations of State and Political Subdivisions [Member]
Contractual Maturities of Investment Securities [Line Items]
Available-for-sale securities, maturing in one year or less, amortized cost	[6],[7]	$ 149
Available-for-sale securities, maturing after one year through five years, amortized cost	[6],[7]	2,539
Available-for-sale securities, maturing after five years through ten years, amortized cost	[6],[7]	1,542
Available-for-sale securities, maturing after ten years, amortized cost	[6],[7]	6,861
Available-for-sale securities, Amortized Cost		11,091	[6],[7]	11,484
Available-for-sale securities, maturing in one year or less, fair value	[6],[7]	149
Available-for-sale securities, maturing after one year through five years, fair value	[6],[7]	2,510
Available-for-sale securities, maturing after five years through ten years, fair value	[6],[7]	1,470
Available-for-sale securities, maturing after ten years, fair value	[6],[7]	5,815
Available-for-sale securities, total, fair value		$ 9,944	[6],[7]	10,125
Available-for-sale securities, maturing in one year or less, weighted-average maturity in years	[6],[7]	3 months 18 days
Available-for-sale securities, maturing after one year through five years, weighted-average maturity in years	[6],[7]	3 years 6 months
Available-for-sale securities, maturing after five years through ten years, weighted-average maturity in years	[6],[7]	7 years 9 months 18 days
Available-for-sale securities, maturing after ten years, weighted- average maturity in years	[6],[7]	16 years 2 months 12 days
Available-for-sale securities, total, weighted-average maturity in years	[6],[7]	11 years 10 months 24 days
Available-for-sale securities, maturing in one year or less, weighted-average yield	[4],[6],[7]	5.76%
Available-for-sale securities, maturing after one year through five years, weighted-average yield	[4],[6],[7]	4.68%
Available-for-sale securities, maturing after five years through ten years, weighted-average yield	[4],[6],[7]	3.99%
Available-for-sale securities, maturing after ten years, weighted-average yield	[4],[6],[7]	3.37%
Available-for-sale securities, total, weighted-average yield	[4],[6],[7]	3.79%
Other [Member]
Contractual Maturities of Investment Securities [Line Items]
Available-for-sale securities, maturing after one year through five years, amortized cost		$ 4
Available-for-sale securities, Amortized Cost		4		6
Available-for-sale securities, maturing after one year through five years, fair value		4
Available-for-sale securities, total, fair value		$ 4		6
Available-for-sale securities, maturing after one year through five years, weighted-average maturity in years		1 year 10 months 24 days
Available-for-sale securities, total, weighted-average maturity in years		1 year 10 months 24 days
Available-for-sale securities, maturing after one year through five years, weighted-average yield	[4]	1.89%
Available-for-sale securities, total, weighted-average yield	[4]	1.89%
Excluding Portfolio Level Basis Adjustments [Member]
Contractual Maturities of Investment Securities [Line Items]
Available-for-sale securities, Amortized Cost		$ 76,889	[1],[3]	81,450
Available-for-sale securities, total, fair value		$ 69,221		$ 72,910

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

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

[3] 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.

[4] Weighted-average yields for obligations of state and political subdivisions are presented on a fully-taxable equivalent basis based on a federal income tax rate of 21 percent. Yields on investment securities are computed based on amortized cost balances, excluding any premiums or discounts recorded related to the transfer of investment securities at fair value from available-for-sale to held-to-maturity.

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

[6] 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.

[7] 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.