Loans - Consumer, Excluding Credit Card Loan Portfolio, Residential Real Estate, Nonaccrual Loans and Other Credit Quality Indicators (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 1,264,093	$ 1,084,850	$ 1,280,870
Consumer, excluding credit card
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	389,592	300,447	397,275
Consumer, excluding credit card | Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	3,449		3,466
Retained loans	$ 319,984		$ 326,409
Weighted average LTV ratio	48.00%		49.00%
Weighted average FICO	776		770
Approximate percentage of Chapter 7 loans 30 days or more past due	9.00%
Interest income on nonaccrual loans recognized on a cash basis	$ 43	$ 45
Consumer, excluding credit card | Residential real estate | California
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	125,046		$ 127,072
Consumer, excluding credit card | Residential real estate | New York
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	48,175		48,815
Consumer, excluding credit card | Residential real estate | Florida
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	22,371		22,778
Consumer, excluding credit card | Residential real estate | Texas
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	15,106		15,506
Consumer, excluding credit card | Residential real estate | Massachusetts
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	14,014		14,213
Consumer, excluding credit card | Residential real estate | Colorado
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	10,590		10,800
Consumer, excluding credit card | Residential real estate | Illinois
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	10,540		10,856
Consumer, excluding credit card | Residential real estate | Washington
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	9,573		9,923
Consumer, excluding credit card | Residential real estate | New Jersey
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	7,863		8,050
Consumer, excluding credit card | Residential real estate | Connecticut
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	7,020		7,163
Consumer, excluding credit card | Residential real estate | All other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	49,686		51,233
Consumer, excluding credit card | Residential real estate | No FICO/LTV available
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	1,037		989
Consumer, excluding credit card | Residential real estate | Greater than 125% and refreshed FICO scores | Equal to or greater than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	70		72
Consumer, excluding credit card | Residential real estate | Greater than 125% and refreshed FICO scores | Less than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	0		0
Consumer, excluding credit card | Residential real estate | 101% to 125% and refreshed FICO scores | Equal to or greater than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	228		223
Consumer, excluding credit card | Residential real estate | 101% to 125% and refreshed FICO scores | Less than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	5		4
Consumer, excluding credit card | Residential real estate | 80% to 100% and refreshed FICO scores | Equal to or greater than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	6,533		6,491
Consumer, excluding credit card | Residential real estate | 80% to 100% and refreshed FICO scores | Less than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	102		102
Consumer, excluding credit card | Residential real estate | Lower than 80% and refreshed FICO scores | Equal to or greater than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	302,573		309,251
Consumer, excluding credit card | Residential real estate | Lower than 80% and refreshed FICO scores | Less than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 9,436		$ 9,277