Loans - Consumer Banking Portfolio by Credit Quality Indicator (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 280,466	$ 277,340
Consumer Banking
Financing Receivable, Credit Quality Indicator [Line Items]
Term loans by vintage year one	11,666	38,021
Term loans by vintage year two	34,559	18,865
Term loans by vintage year three	16,633	10,789
Term loans by vintage year four	9,342	5,487
Term loans by vintage year five	4,604	2,816
Term loans by vintage after year five	3,170	1,287
Total term loans	79,974	77,265
Revolving loans	348	373
Revolving loans converted to term	8	8
Total	80,330	77,646
Auto \| Consumer Banking
Financing Receivable, Credit Quality Indicator [Line Items]
Term loans by vintage year one	11,555	37,736
Term loans by vintage year two	34,363	18,687
Term loans by vintage year three	16,516	10,615
Term loans by vintage year four	9,181	5,318
Term loans by vintage year five	4,446	2,639
Term loans by vintage after year five	2,543	784
Total term loans	78,604	75,779
Revolving loans	0	0
Revolving loans converted to term	0	0
Total	78,604	75,779
Retail banking \| Consumer Banking
Financing Receivable, Credit Quality Indicator [Line Items]
Term loans by vintage year one	111	285
Term loans by vintage year two	196	178
Term loans by vintage year three	117	174
Term loans by vintage year four	161	169
Term loans by vintage year five	158	177
Term loans by vintage after year five	627	503
Total term loans	1,370	1,486
Revolving loans	348	373
Revolving loans converted to term	8	8
Total	1,726	1,867
PPP loans	112	232
Current \| Retail banking \| Consumer Banking
Financing Receivable, Credit Quality Indicator [Line Items]
Term loans by vintage year one	111	285
Term loans by vintage year two	195	171
Term loans by vintage year three	114	172
Term loans by vintage year four	161	161
Term loans by vintage year five	155	176
Term loans by vintage after year five	614	491
Total term loans	1,350	1,456
Revolving loans	336	345
Revolving loans converted to term	6	6
Total	1,692	1,807
30-59 days \| Retail banking \| Consumer Banking
Financing Receivable, Credit Quality Indicator [Line Items]
Term loans by vintage year one	0	0
Term loans by vintage year two	0	2
Term loans by vintage year three	1	2
Term loans by vintage year four	0	7
Term loans by vintage year five	0	0
Term loans by vintage after year five	1	1
Total term loans	2	12
Revolving loans	7	23
Revolving loans converted to term	0	0
Total	9	35
60-89 days \| Retail banking \| Consumer Banking
Financing Receivable, Credit Quality Indicator [Line Items]
Term loans by vintage year one	0	0
Term loans by vintage year two	1	4
Term loans by vintage year three	2	0
Term loans by vintage year four	0	0
Term loans by vintage year five	0	0
Term loans by vintage after year five	0	2
Total term loans	3	6
Revolving loans	2	1
Revolving loans converted to term	0	0
Total	5	7
Greater than 90 days \| Retail banking \| Consumer Banking
Financing Receivable, Credit Quality Indicator [Line Items]
Term loans by vintage year one	0	0
Term loans by vintage year two	0	1
Term loans by vintage year three	0	0
Term loans by vintage year four	0	1
Term loans by vintage year five	3	1
Term loans by vintage after year five	12	9
Total term loans	15	12
Revolving loans	3	4
Revolving loans converted to term	2	2
Total	20	18
Greater than 660 \| Auto \| Consumer Banking
Financing Receivable, Credit Quality Indicator [Line Items]
Term loans by vintage year one	6,942	20,758
Term loans by vintage year two	18,859	8,630
Term loans by vintage year three	7,644	4,739
Term loans by vintage year four	4,089	2,394
Term loans by vintage year five	1,978	1,153
Term loans by vintage after year five	1,052	301
Total term loans	40,564	37,975
Revolving loans	0	0
Revolving loans converted to term	0	0
Total	40,564	37,975
621-660 \| Auto \| Consumer Banking
Financing Receivable, Credit Quality Indicator [Line Items]
Term loans by vintage year one	2,124	7,456
Term loans by vintage year two	6,797	3,721
Term loans by vintage year three	3,276	2,109
Term loans by vintage year four	1,820	1,084
Term loans by vintage year five	909	537
Term loans by vintage after year five	520	157
Total term loans	15,446	15,064
Revolving loans	0	0
Revolving loans converted to term	0	0
Total	15,446	15,064
620 or below \| Auto \| Consumer Banking
Financing Receivable, Credit Quality Indicator [Line Items]
Term loans by vintage year one	2,489	9,522
Term loans by vintage year two	8,707	6,336
Term loans by vintage year three	5,596	3,767
Term loans by vintage year four	3,272	1,840
Term loans by vintage year five	1,559	949
Term loans by vintage after year five	971	326
Total term loans	22,594	22,740
Revolving loans	0	0
Revolving loans converted to term	0	0
Total	$ 22,594	$ 22,740

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