Investment Securities - Amortized Cost, Fair Value and Yield by Maturity Date (Detail) - USD ($) $ in Millions		3 Months Ended		12 Months Ended
		Mar. 31, 2023		Dec. 31, 2022
Contractual Maturities of Investment Securities [Line Items]
Available-for-sale securities, Amortized Cost		$ 72,696	[1]	$ 81,450
Available-for-sale securities, total, fair value	[2]	$ 65,491	[1]	$ 72,910
Available-for-sale securities, total, weighted-average maturity in years		7 years	[1]	7 years 4 months 24 days
Available-for-sale securities, total, weighted-average yield		2.82%	[1],[3]	2.94%
Held-to-maturity securities, Amortized Cost		$ 88,462	[1]	$ 88,740
Held-to-maturity securities, total, fair value		$ 78,876	[1]	$ 77,874
Held-to-maturity securities, total, weighted-average maturity in years	[1]	8 years 10 months 24 days
Held-to-maturity securities, total, weighted-average yield		2.24%	[1]	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	[1]	$ 261
Available-for-sale securities, maturing after one year through five years, amortized cost	[1]	4,452
Available-for-sale securities, maturing after five years through ten years, amortized cost	[1]	13,339
Available-for-sale securities, maturing after ten years, amortized cost	[1]	2,369
Available-for-sale securities, Amortized Cost		20,421	[1]	$ 24,801
Available-for-sale securities, maturing in one year or less, fair value	[1]	261
Available-for-sale securities, maturing after one year through five years, fair value	[1]	4,114
Available-for-sale securities, maturing after five years through ten years, fair value	[1]	11,829
Available-for-sale securities, maturing after ten years, fair value	[1]	1,850
Available-for-sale securities, total, fair value		$ 18,054	[1]	22,033
Available-for-sale securities, maturing in one year or less, weighted-average maturity in years	[1]	2 months 12 days
Available-for-sale securities, maturing after one year through five years, weighted-average maturity in years	[1]	3 years 10 months 24 days
Available-for-sale securities, maturing after five years through ten years, weighted-average maturity in years	[1]	7 years
Available-for-sale securities, maturing after ten years, weighted- average maturity in years	[1]	11 years 2 months 12 days
Available-for-sale securities, total, weighted-average maturity in years	[1]	6 years 8 months 12 days
Available-for-sale securities, maturing in one year or less, weighted-average yield	[1],[3]	4.75%
Available-for-sale securities, maturing after one year through five years, weighted-average yield	[1],[3]	1.70%
Available-for-sale securities, maturing after five years through ten years, weighted-average yield	[1],[3]	1.93%
Available-for-sale securities, maturing after ten years, weighted-average yield	[1],[3]	2.00%
Available-for-sale securities, total, weighted-average yield	[1],[3]	1.92%
Held-to-maturity securities, maturing after one year through five years, amortized cost		$ 1,344
Held-to-maturity securities, Amortized Cost		1,344		1,344
Held-to-maturity securities, maturing after one year through five years, fair value		1,307
Held-to-maturity securities, total, fair value		$ 1,307		1,293
Held-to-maturity securities, maturing after one year through five years, weighted-average maturity in years		3 years
Held-to-maturity securities, total, weighted-average maturity in years		3 years
Held-to-maturity securities, maturing after one year through five years, weighted-average yield	[3]	2.85%
Held-to-maturity securities, total, weighted-average yield	[3]	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	[4]	$ 71
Available-for-sale securities, maturing after one year through five years, amortized cost	[4]	9,603
Available-for-sale securities, maturing after five years through ten years, amortized cost	[4]	26,252
Available-for-sale securities, maturing after ten years, amortized cost	[4]	1,275
Available-for-sale securities, Amortized Cost	[4]	37,201
Available-for-sale securities, maturing in one year or less, fair value	[4]	70
Available-for-sale securities, maturing after one year through five years, fair value	[4]	9,020
Available-for-sale securities, maturing after five years through ten years, fair value	[4]	23,248
Available-for-sale securities, maturing after ten years, fair value	[4]	1,114
Available-for-sale securities, total, fair value	[4]	$ 33,452
Available-for-sale securities, maturing in one year or less, weighted-average maturity in years	[4]	9 months 18 days
Available-for-sale securities, maturing after one year through five years, weighted-average maturity in years	[4]	3 years 1 month 6 days
Available-for-sale securities, maturing after five years through ten years, weighted-average maturity in years	[4]	7 years 6 months
Available-for-sale securities, maturing after ten years, weighted- average maturity in years	[4]	11 years 1 month 6 days
Available-for-sale securities, total, weighted-average maturity in years	[4]	6 years 6 months
Available-for-sale securities, maturing in one year or less, weighted-average yield	[3],[4]	2.44%
Available-for-sale securities, maturing after one year through five years, weighted-average yield	[3],[4]	2.44%
Available-for-sale securities, maturing after five years through ten years, weighted-average yield	[3],[4]	2.94%
Available-for-sale securities, maturing after ten years, weighted-average yield	[3],[4]	3.55%
Available-for-sale securities, total, weighted-average yield	[3],[4]	2.83%
Held-to-maturity securities, maturing in one year or less, amortized cost	[4]	$ 22
Held-to-maturity securities, maturing after one year through five years, amortized cost	[4]	1,531
Held-to-maturity securities, maturing after five years through ten years, amortized cost	[4]	79,376
Held-to-maturity securities, maturing after ten years, amortized cost	[4]	6,189
Held-to-maturity securities, Amortized Cost	[4]	87,118
Held-to-maturity securities, maturing in one year or less, fair value	[4]	21
Held-to-maturity securities, maturing after one year through five years, fair value	[4]	1,536
Held-to-maturity securities, maturing after five years through ten years, fair value	[4]	70,881
Held-to-maturity securities, maturing after ten years, fair value	[4]	5,131
Held-to-maturity securities, total, fair value	[4]	$ 77,569
Held-to-maturity securities, maturing in one year or less, weighted-average maturity in years	[4]	9 months 18 days
Held-to-maturity securities, maturing after one year through five years, weighted-average maturity in years	[4]	2 years 8 months 12 days
Held-to-maturity securities, maturing after five years through ten years, weighted-average maturity in years	[4]	9 years
Held-to-maturity securities, maturing after ten years, weighted-average maturity in years	[4]	10 years 2 months 12 days
Held-to-maturity securities, total, weighted-average maturity in years	[4]	9 years
Held-to-maturity securities, maturing in one year or less, weighted-average yield	[3]	5.09%
Held-to-maturity securities, maturing after one year through five years, weighted-average yield	[3]	4.58%
Held-to-maturity securities, maturing after five years through ten years, weighted-average yield	[3]	2.20%
Held-to-maturity securities, maturing after ten years, weighted-average yield	[3]	1.93%
Held-to-maturity securities, total, weighted-average yield	[3]	2.23%
Asset-Backed Securities [Member]
Contractual Maturities of Investment Securities [Line Items]
Available-for-sale securities, maturing in one year or less, amortized cost		$ 3,054
Available-for-sale securities, maturing after one year through five years, amortized cost		506
Available-for-sale securities, maturing after five years through ten years, amortized cost		276
Available-for-sale securities, Amortized Cost		3,836		4,356
Available-for-sale securities, maturing in one year or less, fair value		3,021
Available-for-sale securities, maturing after one year through five years, fair value		509
Available-for-sale securities, maturing after five years through ten years, fair value		277
Available-for-sale securities, total, fair value		$ 3,807		4,323
Available-for-sale securities, maturing in one year or less, weighted-average maturity in years		4 months 24 days
Available-for-sale securities, maturing after one year through five years, weighted-average maturity in years		3 years 2 months 12 days
Available-for-sale securities, maturing after five years through ten years, weighted-average maturity in years		5 years 8 months 12 days
Available-for-sale securities, total, weighted-average maturity in years		1 year 2 months 12 days
Available-for-sale securities, maturing in one year or less, weighted-average yield	[3]	4.25%
Available-for-sale securities, maturing after one year through five years, weighted-average yield	[3]	6.94%
Available-for-sale securities, maturing after five years through ten years, weighted-average yield	[3]	5.77%
Available-for-sale securities, total, weighted-average yield	[3]	4.72%
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	[5],[6]	$ 152
Available-for-sale securities, maturing after one year through five years, amortized cost	[5],[6]	3,579
Available-for-sale securities, maturing after five years through ten years, amortized cost	[5],[6]	1,556
Available-for-sale securities, maturing after ten years, amortized cost	[5],[6]	5,947
Available-for-sale securities, Amortized Cost		11,234	[5],[6]	11,484
Available-for-sale securities, maturing in one year or less, fair value	[5],[6]	153
Available-for-sale securities, maturing after one year through five years, fair value	[5],[6]	3,550
Available-for-sale securities, maturing after five years through ten years, fair value	[5],[6]	1,488
Available-for-sale securities, maturing after ten years, fair value	[5],[6]	4,983
Available-for-sale securities, total, fair value		$ 10,174	[5],[6]	10,125
Available-for-sale securities, maturing in one year or less, weighted-average maturity in years	[5],[6]	3 months 18 days
Available-for-sale securities, maturing after one year through five years, weighted-average maturity in years	[5],[6]	3 years 8 months 12 days
Available-for-sale securities, maturing after five years through ten years, weighted-average maturity in years	[5],[6]	7 years 9 months 18 days
Available-for-sale securities, maturing after ten years, weighted- average maturity in years	[5],[6]	16 years 2 months 12 days
Available-for-sale securities, total, weighted-average maturity in years	[5],[6]	10 years 9 months 18 days
Available-for-sale securities, maturing in one year or less, weighted-average yield	[3],[5],[6]	5.12%
Available-for-sale securities, maturing after one year through five years, weighted-average yield	[3],[5],[6]	4.51%
Available-for-sale securities, maturing after five years through ten years, weighted-average yield	[3],[5],[6]	3.89%
Available-for-sale securities, maturing after ten years, weighted-average yield	[3],[5],[6]	3.21%
Available-for-sale securities, total, weighted-average yield	[3],[5],[6]	3.74%
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		2 years 2 months 12 days
Available-for-sale securities, total, weighted-average maturity in years		2 years 2 months 12 days
Available-for-sale securities, maturing after one year through five years, weighted-average yield	[3]	1.89%
Available-for-sale securities, total, weighted-average yield	[3]	1.89%

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

[3] 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.

[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.