Fair Value Measurements - Carrying Value and Estimated Fair Value of Financial Instruments (Detail) - USD ($) $ in Millions		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Federal funds sold and securities purchased under agreements to resell	[1]	$ 10,514	$ 35,746
Loans, net of allowance for credit losses		55,417	61,073	$ 67,916
Loans held for sale	[1]	4,217	337
Deposits		143,032	145,150	$ 119,693
Long-term debt	[1]	17,236	19,979
Commercial loans:
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans held for sale		461	129
Consumer loans:
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans held for sale		3,756	208
Level 1
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Short-term financial assets, net of allowance for credit losses		954	1,302
Federal funds sold and securities purchased under agreements to resell		0	0
Securities held-to-maturity, net of allowance for credit losses		0	0
Short-term financial liabilities		0	0
Deposits		0	0
Deposits held for sale		0
Long-term debt		0	0
Level 1 | Commercial loans:
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans, net of allowance for credit losses		0	0
Loans held for sale		0	0
Level 1 | Consumer loans:
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans, net of allowance for credit losses		0	0
Loans held for sale		0	0
Level 2
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Short-term financial assets, net of allowance for credit losses		47,400	14,353
Federal funds sold and securities purchased under agreements to resell		10,514	35,746
Securities held-to-maturity, net of allowance for credit losses		5,359	9,369
Short-term financial liabilities		6,338	4,952
Deposits		131,533	141,001
Deposits held for sale		8,750
Long-term debt		8,861	9,720
Level 2 | Commercial loans:
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans, net of allowance for credit losses		0	0
Loans held for sale		359	93
Level 2 | Consumer loans:
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans, net of allowance for credit losses		0	0
Loans held for sale		77	217
Level 3
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Short-term financial assets, net of allowance for credit losses		50	12
Federal funds sold and securities purchased under agreements to resell		0	0
Securities held-to-maturity, net of allowance for credit losses		0	0
Short-term financial liabilities		51	13
Deposits		0	0
Deposits held for sale		0
Long-term debt		0	0
Level 3 | Commercial loans:
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans, net of allowance for credit losses		39,862	41,417
Loans held for sale		84	0
Level 3 | Consumer loans:
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans, net of allowance for credit losses		15,672	19,865
Loans held for sale		3,732	0
Carrying Value
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Short-term financial assets, net of allowance for credit losses		48,404	15,667
Federal funds sold and securities purchased under agreements to resell		10,514	35,746
Securities held-to-maturity, net of allowance for credit losses		5,203	8,981
Short-term financial liabilities		6,389	4,965
Deposits		131,533	140,995
Deposits held for sale		8,750
Long-term debt		8,294	9,254
Carrying Value | Commercial loans:
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans, net of allowance for credit losses		39,376	40,785
Loans held for sale		438	93
Carrying Value | Consumer loans:
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans, net of allowance for credit losses		16,041	20,256
Loans held for sale		3,731	208
Fair Value
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Short-term financial assets, net of allowance for credit losses		48,404	15,667
Federal funds sold and securities purchased under agreements to resell		10,514	35,746
Securities held-to-maturity, net of allowance for credit losses		5,359	9,369
Short-term financial liabilities		6,389	4,965
Deposits		131,533	141,001
Deposits held for sale		8,750
Long-term debt		8,861	9,720
Fair Value | Commercial loans:
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans, net of allowance for credit losses		39,862	41,417
Loans held for sale		443	93
Fair Value | Consumer loans:
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans, net of allowance for credit losses		15,672	19,865
Loans held for sale		$ 3,809	$ 217

[1] The following table summarizes assets and liabilities related to our consolidated variable interest entities ("VIEs") at December 31, 2021 and 2020. Assets and liabilities exclude intercompany balances that eliminate in consolidation. See Note 27, "Variable Interest Entities," for additional information. At December 31,20212020(in millions)AssetsLoans$46 $10 Other assets55 79 Total assets$101 $89 LiabilitiesInterest, taxes and other liabilities$9 $10 Total liabilities$9 $10