Investment Securities - Amortized Cost, Fair Value and Yield by Maturity Date (Detail) - USD ($) $ in Millions		6 Months Ended		12 Months Ended
		Jun. 30, 2022		Dec. 31, 2021
Contractual Maturities of Investment Securities [Line Items]
Available-for-sale securities, Amortized Cost		$ 108,255		$ 132,241
Available-for-sale securities, total, fair value	[1]	$ 98,806		$ 132,963
Available-for-sale securities, total, weighted-average maturity in years		8 years 2 months 12 days	[2]	5 years 6 months
Available-for-sale securities, total, weighted-average yield		2.13%	[2],[3]	1.73%
Held-to-maturity securities, Amortized Cost		$ 61,503	[2]	$ 41,858
Held-to-maturity securities, total, fair value		$ 55,657	[2]	$ 41,812
Held-to-maturity securities, total, weighted-average maturity in years	[2]	9 years 9 months 18 days
Held-to-maturity securities, total, weighted-average yield		1.94%	[2]	1.45%
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		$ 1,826
Available-for-sale securities, maturing after one year through five years, amortized cost		3,525
Available-for-sale securities, maturing after five years through ten years, amortized cost		17,771
Available-for-sale securities, maturing after ten years, amortized cost		2,657
Available-for-sale securities, Amortized Cost		25,779		$ 36,648
Available-for-sale securities, maturing in one year or less, fair value		1,824
Available-for-sale securities, maturing after one year through five years, fair value		3,296
Available-for-sale securities, maturing after five years through ten years, fair value		16,479
Available-for-sale securities, maturing after ten years, fair value		2,168
Available-for-sale securities, total, fair value		$ 23,767		36,609
Available-for-sale securities, maturing in one year or less, weighted-average maturity in years		3 months 18 days
Available-for-sale securities, maturing after one year through five years, weighted-average maturity in years		4 years 4 months 24 days
Available-for-sale securities, maturing after five years through ten years, weighted-average maturity in years		7 years 4 months 24 days
Available-for-sale securities, maturing after ten years, weighted- average maturity in years		11 years 9 months 18 days
Available-for-sale securities, total, weighted-average maturity in years		6 years 10 months 24 days
Available-for-sale securities, maturing in one year or less, weighted-average yield	[3]	1.96%
Available-for-sale securities, maturing after one year through five years, weighted-average yield	[3]	1.50%
Available-for-sale securities, maturing after five years through ten years, weighted-average yield	[3]	2.04%
Available-for-sale securities, maturing after ten years, weighted-average yield	[3]	1.99%
Available-for-sale securities, total, weighted-average yield	[3]	1.95%
Held-to-maturity securities, maturing after one year through five years, amortized cost		$ 1,343
Held-to-maturity securities, Amortized Cost		1,343
Held-to-maturity securities, maturing after one year through five years, fair value		1,337
Held-to-maturity securities, total, fair value		$ 1,337
Held-to-maturity securities, maturing after one year through five years, weighted-average maturity in years		3 years 9 months 18 days
Held-to-maturity securities, total, weighted-average maturity in years		3 years 9 months 18 days
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]	$ 44
Available-for-sale securities, maturing after one year through five years, amortized cost	[4]	12,785
Available-for-sale securities, maturing after five years through ten years, amortized cost	[4]	33,303
Available-for-sale securities, maturing after ten years, amortized cost	[4]	25,412
Available-for-sale securities, Amortized Cost	[4]	71,544
Available-for-sale securities, maturing in one year or less, fair value	[4]	44
Available-for-sale securities, maturing after one year through five years, fair value	[4]	12,381
Available-for-sale securities, maturing after five years through ten years, fair value	[4]	30,454
Available-for-sale securities, maturing after ten years, fair value	[4]	22,437
Available-for-sale securities, total, fair value	[4]	$ 65,316
Available-for-sale securities, maturing in one year or less, weighted-average maturity in years	[4]	8 months 12 days
Available-for-sale securities, maturing after one year through five years, weighted-average maturity in years	[4]	3 years 2 months 12 days
Available-for-sale securities, maturing after five years through ten years, weighted-average maturity in years	[4]	7 years 10 months 24 days
Available-for-sale securities, maturing after ten years, weighted- average maturity in years	[4]	10 years 7 months 6 days
Available-for-sale securities, total, weighted-average maturity in years	[4]	8 years
Available-for-sale securities, maturing in one year or less, weighted-average yield	[4]	2.67%
Available-for-sale securities, maturing after one year through five years, weighted-average yield	[4]	2.03%
Available-for-sale securities, maturing after five years through ten years, weighted-average yield	[4]	1.81%
Available-for-sale securities, maturing after ten years, weighted-average yield	[4]	2.11%
Available-for-sale securities, total, weighted-average yield	[4]	1.96%
Held-to-maturity securities, maturing after five years through ten years, amortized cost	[4]	$ 23,977
Held-to-maturity securities, maturing after ten years, amortized cost	[4]	36,183
Held-to-maturity securities, Amortized Cost	[4]	60,160
Held-to-maturity securities, maturing after five years through ten years, fair value	[4]	22,825
Held-to-maturity securities, maturing after ten years, fair value	[4]	31,495
Held-to-maturity securities, total, fair value	[4]	$ 54,320
Held-to-maturity securities, maturing after five years through ten years, weighted-average maturity in years	[4]	9 years 1 month 6 days
Held-to-maturity securities, maturing after ten years, weighted-average maturity in years	[4]	10 years 7 months 6 days
Held-to-maturity securities, total, weighted-average maturity in years	[4]	10 years
Held-to-maturity securities, maturing after five years through ten years, weighted-average yield	[3],[4]	2.22%
Held-to-maturity securities, maturing after ten years, weighted-average yield	[3],[4]	1.72%
Held-to-maturity securities, total, weighted-average yield	[3],[4]	1.92%
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]	$ 182
Available-for-sale securities, maturing after one year through five years, amortized cost	[5],[6]	1,974
Available-for-sale securities, maturing after five years through ten years, amortized cost		1,480
Available-for-sale securities, maturing after ten years, amortized cost		7,289
Available-for-sale securities, Amortized Cost		10,925		10,130
Available-for-sale securities, maturing in one year or less, fair value		182
Available-for-sale securities, maturing after one year through five years, fair value		1,955
Available-for-sale securities, maturing after five years through ten years, fair value		1,401
Available-for-sale securities, maturing after ten years, fair value		6,178
Available-for-sale securities, total, fair value		$ 9,716		10,717
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]	4 years
Available-for-sale securities, maturing after five years through ten years, weighted-average maturity in years	[5],[6]	7 years 2 months 12 days
Available-for-sale securities, maturing after ten years, weighted- average maturity in years	[5],[6]	16 years 10 months 24 days
Available-for-sale securities, total, weighted-average maturity in years	[5],[6]	13 years
Available-for-sale securities, maturing in one year or less, weighted-average yield	[3],[5],[6]	4.63%
Available-for-sale securities, maturing after one year through five years, weighted-average yield	[3],[5],[6]	4.43%
Available-for-sale securities, maturing after five years through ten years, weighted-average yield	[3],[5],[6]	3.82%
Available-for-sale securities, maturing after ten years, weighted-average yield	[3],[5],[6]	3.36%
Available-for-sale securities, total, weighted-average yield	[3],[5],[6]	3.64%
Other [Member]
Contractual Maturities of Investment Securities [Line Items]
Available-for-sale securities, maturing after one year through five years, amortized cost		$ 7
Available-for-sale securities, Amortized Cost		7		7
Available-for-sale securities, maturing after one year through five years, fair value		7
Available-for-sale securities, total, fair value		$ 7		$ 7
Available-for-sale securities, maturing after one year through five years, weighted-average maturity in years		2 years 10 months 24 days
Available-for-sale securities, total, weighted-average maturity in years		2 years 10 months 24 days
Available-for-sale securities, maturing after one year through five years, weighted-average yield	[3]	2.07%
Available-for-sale securities, total, weighted-average yield	[3]	2.07%

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

[2] 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.

[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.