Loans - Consumer, Excluding Credit Card Loan Portfolio, Auto and Other, Nonaccrual Loans and Other Credit Quality Indicators (Details) - USD ($)	Jun. 30, 2022	Dec. 31, 2021	Jun. 30, 2021
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	$ 1,052,390,000,000	$ 1,010,206,000,000	$ 963,665,000,000
Consumer, excluding credit card
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	302,631,000,000	295,556,000,000	$ 297,731,000,000
Consumer, excluding credit card | Auto and other
Financing Receivable, Credit Quality Indicator [Line Items]
Nonaccrual loans	110,000,000	119,000,000
Retained loans	65,489,000,000	70,761,000,000
Consumer, excluding credit card | Auto and other | Paycheck Protection Program (PPP)
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	1,500,000,000	5,400,000,000
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	81,000,000	35,000,000
Retained loans	86,000,000	506,000,000
Consumer, excluding credit card | Auto and other | California
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	10,344,000,000	11,163,000,000
Consumer, excluding credit card | Auto and other | Texas
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	7,446,000,000	7,859,000,000
Consumer, excluding credit card | Auto and other | Florida
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	4,845,000,000	4,901,000,000
Consumer, excluding credit card | Auto and other | New York
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	4,625,000,000	5,848,000,000
Consumer, excluding credit card | Auto and other | Illinois
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	2,718,000,000	2,930,000,000
Consumer, excluding credit card | Auto and other | New Jersey
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	2,232,000,000	2,355,000,000
Consumer, excluding credit card | Auto and other | Pennsylvania
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	1,869,000,000	2,004,000,000
Consumer, excluding credit card | Auto and other | Georgia
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	1,719,000,000	1,748,000,000
Consumer, excluding credit card | Auto and other | Louisiana
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	1,693,000,000	1,801,000,000
Consumer, excluding credit card | Auto and other | Arizona
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	1,681,000,000	1,887,000,000
Consumer, excluding credit card | Auto and other | All other
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	$ 26,317,000,000	$ 28,265,000,000