Loans - Consumer, Excluding Credit Card Loan Portfolio, Auto and Other, Nonaccrual Loans and Other Credit Quality Indicators (Details) - USD ($)	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	$ 1,018,397,000,000	$ 1,010,206,000,000	$ 948,642,000,000
Consumer, excluding credit card
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	296,161,000,000	295,556,000,000	$ 302,392,000,000
Consumer, excluding credit card | Auto and other
Financing Receivable, Credit Quality Indicator [Line Items]
Nonaccrual loans	110,000,000	119,000,000
Retained loans	68,235,000,000	70,761,000,000
Consumer, excluding credit card | Auto and other | Paycheck Protection Program (PPP)
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	2,900,000,000	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	163,000,000	35,000,000
Retained loans	179,000,000	506,000,000
Consumer, excluding credit card | Auto and other | California
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	10,794,000,000	11,163,000,000
Consumer, excluding credit card | Auto and other | Texas
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	7,725,000,000	7,859,000,000
Consumer, excluding credit card | Auto and other | New York
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	5,075,000,000	5,848,000,000
Consumer, excluding credit card | Auto and other | Florida
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	4,929,000,000	4,901,000,000
Consumer, excluding credit card | Auto and other | Illinois
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	2,785,000,000	2,930,000,000
Consumer, excluding credit card | Auto and other | New Jersey
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	2,274,000,000	2,355,000,000
Consumer, excluding credit card | Auto and other | Pennsylvania
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	1,936,000,000	2,004,000,000
Consumer, excluding credit card | Auto and other | Arizona
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	1,789,000,000	1,887,000,000
Consumer, excluding credit card | Auto and other | Louisiana
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	1,771,000,000	1,801,000,000
Consumer, excluding credit card | Auto and other | Georgia
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	1,760,000,000	1,748,000,000
Consumer, excluding credit card | Auto and other | All other
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	$ 27,397,000,000	$ 28,265,000,000