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, 2026	Mar. 31, 2025	Dec. 31, 2025
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 1,425,236	$ 1,300,990	$ 1,408,905
Consumer, excluding credit card
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	367,274	372,892	368,741
Consumer, excluding credit card | Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	3,574		3,632
Total retained loans	$ 301,947		$ 303,531
Weighted average LTV ratio	47.00%		48.00%
Weighted average FICO	775		775
Approximate percentage of Chapter 7 loans 30 days or more past due	10.00%
Interest income on nonaccrual loans recognized on a cash basis	$ 36	$ 37
Consumer, excluding credit card | Residential real estate | California
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	116,392		$ 117,500
Consumer, excluding credit card | Residential real estate | New York
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	46,141		46,378
Consumer, excluding credit card | Residential real estate | Florida
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	21,930		21,864
Consumer, excluding credit card | Residential real estate | Texas
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	14,398		14,398
Consumer, excluding credit card | Residential real estate | Massachusetts
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	12,923		12,985
Consumer, excluding credit card | Residential real estate | Colorado
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	10,319		10,316
Consumer, excluding credit card | Residential real estate | Washington
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	9,282		9,408
Consumer, excluding credit card | Residential real estate | Illinois
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	9,020		9,152
Consumer, excluding credit card | Residential real estate | New Jersey
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	7,479		7,486
Consumer, excluding credit card | Residential real estate | Connecticut
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	6,823		6,823
Consumer, excluding credit card | Residential real estate | All other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	47,240		47,221
Consumer, excluding credit card | Residential real estate | No FICO/LTV available
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	653		690
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]
Total retained loans	86		71
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]
Total retained loans	6		4
Consumer, excluding credit card | Residential real estate | Greater than 100% but less than or equal to 125% and refreshed FICO scores | Equal to or greater than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	214		282
Consumer, excluding credit card | Residential real estate | Greater than 100% but less than or equal to 125% and refreshed FICO scores | Less than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	4		5
Consumer, excluding credit card | Residential real estate | Greater than 80% but less than or equal to 100% and refreshed FICO scores | Equal to or greater than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	4,659		5,990
Consumer, excluding credit card | Residential real estate | Greater than 80% but less than or equal to 100% and refreshed FICO scores | Less than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	104		131
Consumer, excluding credit card | Residential real estate | Less than or equal to 80% and refreshed FICO scores | Equal to or greater than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	287,515		287,923
Consumer, excluding credit card | Residential real estate | Less than or equal to 80% and refreshed FICO scores | Less than 660
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 8,706		$ 8,435