Loans - Consumer Banking Portfolio by Credit Quality Indicator (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 311,323	$ 312,331
Consumer Banking:
Financing Receivable, Credit Quality Indicator [Line Items]
2023	12,730	31,969
2022	27,070	25,937
2021	21,285	11,591
2020	9,028	6,039
2019	4,387	2,589
Prior	2,381	1,372
Total Term Loans	76,881	79,497
Revolving Loans	393	422
Revolving Loans Converted to Term	6	6
Total	77,280	79,925
Auto | Consumer Banking:
Financing Receivable, Credit Quality Indicator [Line Items]
2023	12,676	31,801
2022	26,917	25,807
2021	21,191	11,509
2020	8,955	5,906
2019	4,264	2,459
Prior	1,838	891
Total Term Loans	75,841	78,373
Revolving Loans	0	0
Revolving Loans Converted to Term	0	0
Total	75,841	78,373
Retail banking | Consumer Banking:
Financing Receivable, Credit Quality Indicator [Line Items]
2023	54	168
2022	153	130
2021	94	82
2020	73	133
2019	123	130
Prior	543	481
Total Term Loans	1,040	1,124
Revolving Loans	393	422
Revolving Loans Converted to Term	6	6
Total	1,439	1,552
Current | Retail banking | Consumer Banking:
Financing Receivable, Credit Quality Indicator [Line Items]
2023	54	166
2022	150	128
2021	94	82
2020	72	133
2019	123	127
Prior	530	470
Total Term Loans	1,023	1,106
Revolving Loans	379	408
Revolving Loans Converted to Term	5	4
Total	1,407	1,518
30-59 days | Retail banking | Consumer Banking:
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0	2
2022	3	1
2021	0	0
2020	1	0
2019	0	0
Prior	3	2
Total Term Loans	7	5
Revolving Loans	7	8
Revolving Loans Converted to Term	0	0
Total	14	13
60-89 days | Retail banking | Consumer Banking:
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0	0
2022	0	1
2021	0	0
2020	0	0
2019	0	0
Prior	1	1
Total Term Loans	1	2
Revolving Loans	3	2
Revolving Loans Converted to Term	0	0
Total	4	4
Greater than 90 days | Retail banking | Consumer Banking:
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0	0
2022	0	0
2021	0	0
2020	0	0
2019	0	3
Prior	9	8
Total Term Loans	9	11
Revolving Loans	4	4
Revolving Loans Converted to Term	1	2
Total	14	17
Greater than 660 | Auto | Consumer Banking:
Financing Receivable, Credit Quality Indicator [Line Items]
2023	6,319	17,872
2022	15,029	14,246
2021	11,726	5,354
2020	4,147	2,595
2019	1,828	1,032
Prior	695	328
Total Term Loans	39,744	41,427
Revolving Loans	0	0
Revolving Loans Converted to Term	0	0
Total	39,744	41,427
621-660 | Auto | Consumer Banking:
Financing Receivable, Credit Quality Indicator [Line Items]
2023	2,632	6,212
2022	5,284	5,060
2021	4,145	2,257
2020	1,756	1,167
2019	850	513
Prior	388	185
Total Term Loans	15,055	15,394
Revolving Loans	0	0
Revolving Loans Converted to Term	0	0
Total	15,055	15,394
620 or below | Auto | Consumer Banking:
Financing Receivable, Credit Quality Indicator [Line Items]
2023	3,725	7,717
2022	6,604	6,501
2021	5,320	3,898
2020	3,052	2,144
2019	1,586	914
Prior	755	378
Total Term Loans	21,042	21,552
Revolving Loans	0	0
Revolving Loans Converted to Term	0	0
Total	$ 21,042	$ 21,552