Loans - Consumer, Excluding Credit Card Loan Portfolio, Auto and Other, Nonaccrual and Other Credit Quality Indicators and Loan Modifications (Details) - USD ($)	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	$ 1,084,850,000,000	$ 1,089,598,000,000	$ 1,018,397,000,000
Consumer, excluding credit card
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	300,447,000,000	300,753,000,000	$ 296,161,000,000
Consumer, excluding credit card | Auto and other
Financing Receivable, Credit Quality Indicator [Line Items]
Nonaccrual loans	133,000,000	129,000,000
Retained loans	64,332,000,000	63,192,000,000
Additional commitments to lend to borrowers whose loans have been modified as FDM's	0
Consumer, excluding credit card | Auto and other | Not U.S. government-guaranteed
Financing Receivable, Credit Quality Indicator [Line Items]
90 or more days past due and still accruing	0	0
Consumer, excluding credit card | Auto and other | 90 or more days past due | Paycheck Protection Program (PPP)
Financing Receivable, Credit Quality Indicator [Line Items]
Nonaccrual loans	53,000,000	76,000,000
Retained loans	54,000,000	101,000,000
Consumer, excluding credit card | Auto and other | California
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	9,736,000,000	9,689,000,000
Consumer, excluding credit card | Auto and other | Texas
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	7,434,000,000	7,216,000,000
Consumer, excluding credit card | Auto and other | Florida
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	5,013,000,000	4,847,000,000
Consumer, excluding credit card | Auto and other | New York
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	4,411,000,000	4,345,000,000
Consumer, excluding credit card | Auto and other | Illinois
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	2,916,000,000	2,839,000,000
Consumer, excluding credit card | Auto and other | New Jersey
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	2,292,000,000	2,219,000,000
Consumer, excluding credit card | Auto and other | Pennsylvania
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	1,823,000,000	1,822,000,000
Consumer, excluding credit card | Auto and other | Georgia
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	1,760,000,000	1,708,000,000
Consumer, excluding credit card | Auto and other | Ohio
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	1,631,000,000	1,603,000,000
Consumer, excluding credit card | Auto and other | Arizona
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	1,570,000,000	1,551,000,000
Consumer, excluding credit card | Auto and other | All other
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	$ 25,746,000,000	$ 25,353,000,000