Fair Value Measurements - Carrying Value and Estimated Fair Value of Financial Instruments (Detail) - USD ($) $ in Millions		Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Federal funds sold and securities purchased under agreements to resell	[1]	$ 5,759	$ 10,514
Loans, net of allowance for credit losses		58,143		$ 60,673
Loans held for sale	[1]	948	4,217
Deposits		131,175	143,032	$ 148,582
Long-term debt	[1]	15,690	17,236
Commercial loans:
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans held for sale		211	461
Consumer loans:
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans held for sale		737	3,756
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		976	954
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		45,738	47,400
Federal funds sold and securities purchased under agreements to resell		5,759	10,514
Securities held-to-maturity, net of allowance for credit losses		4,758	5,359
Short-term financial liabilities		6,790	6,338
Deposits		128,787	131,533
Deposits held for sale			8,750
Long-term debt		8,611	8,861
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		91	359
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		32	77
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		46	50
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		47	51
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		42,940	39,862
Loans held for sale		0	84
Level 3 | Consumer loans:
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans, net of allowance for credit losses		15,561	15,672
Loans held for sale		683	3,732
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		46,760	48,404
Federal funds sold and securities purchased under agreements to resell		5,759	10,514
Securities held-to-maturity, net of allowance for credit losses		4,804	5,203
Short-term financial liabilities		6,837	6,389
Deposits		128,796	131,533
Deposits held for sale			8,750
Long-term debt		8,025	8,294
Carrying Value | Commercial loans:
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans, net of allowance for credit losses		42,013	39,376
Loans held for sale		91	438
Carrying Value | Consumer loans:
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans, net of allowance for credit losses		16,130	16,041
Loans held for sale		713	3,731
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		46,760	48,404
Federal funds sold and securities purchased under agreements to resell		5,759	10,514
Securities held-to-maturity, net of allowance for credit losses		4,758	5,359
Short-term financial liabilities		6,837	6,389
Deposits		128,787	131,533
Deposits held for sale			8,750
Long-term debt		8,611	8,861
Fair Value | Commercial loans:
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans, net of allowance for credit losses		42,940	39,862
Loans held for sale		91	443
Fair Value | Consumer loans:
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans, net of allowance for credit losses		15,561	15,672
Loans held for sale		$ 715	$ 3,809

[1] The following table summarizes assets and liabilities related to our consolidated variable interest entities ("VIEs") at March 31, 2022 and December 31, 2021. Assets and liabilities exclude intercompany balances that eliminate in consolidation. See Note 17, "Variable Interest Entities," for additional information. March 31, 2022December 31, 2021(in millions)AssetsLoans$128 $46 Other assets51 55 Total assets$179 $101 LiabilitiesInterest, taxes and other liabilities$31 $9 Total liabilities$31 $9