Loans - Consumer, Excluding Credit Card Loan Portfolio, Auto and Other, Nonaccrual and Other Credit Quality Indicators and Loan Modifications (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	$ 1,265,941,000,000	$ 1,068,073,000,000	$ 1,265,941,000,000	$ 1,068,073,000,000	$ 1,089,598,000,000
Consumer, excluding credit card
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	397,054,000,000	301,403,000,000	397,054,000,000	301,403,000,000	300,753,000,000
Consumer, excluding credit card | Auto and other
Financing Receivable, Credit Quality Indicator [Line Items]
Nonaccrual loans	162,000,000		162,000,000		129,000,000
Retained loans	69,419,000,000		69,419,000,000		63,192,000,000
Additional commitments to lend to borrowers whose loans have been modified as FDM's	0	$ 0	0	$ 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		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	33,000,000		33,000,000		76,000,000
Retained loans	35,000,000		35,000,000		101,000,000
Consumer, excluding credit card | Auto and other | California
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	10,580,000,000		10,580,000,000		9,689,000,000
Consumer, excluding credit card | Auto and other | Texas
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	8,280,000,000		8,280,000,000		7,216,000,000
Consumer, excluding credit card | Auto and other | Florida
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	5,500,000,000		5,500,000,000		4,847,000,000
Consumer, excluding credit card | Auto and other | New York
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	4,750,000,000		4,750,000,000		4,345,000,000
Consumer, excluding credit card | Auto and other | Illinois
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	3,095,000,000		3,095,000,000		2,839,000,000
Consumer, excluding credit card | Auto and other | New Jersey
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	2,530,000,000		2,530,000,000		2,219,000,000
Consumer, excluding credit card | Auto and other | Georgia
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	1,892,000,000		1,892,000,000		1,708,000,000
Consumer, excluding credit card | Auto and other | Pennsylvania
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	1,887,000,000		1,887,000,000		1,822,000,000
Consumer, excluding credit card | Auto and other | Arizona
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	1,747,000,000		1,747,000,000		1,551,000,000
Consumer, excluding credit card | Auto and other | North Carolina
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	1,677,000,000		1,677,000,000		1,481,000,000
Consumer, excluding credit card | Auto and other | All other
Financing Receivable, Credit Quality Indicator [Line Items]
Retained loans	$ 27,481,000,000		$ 27,481,000,000		$ 25,475,000,000