Loans - Consumer Banking Portfolio by Credit Quality Indicator (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 277,340	$ 251,624
Consumer Banking
Financing Receivable, Credit Quality Indicator [Line Items]
Term loans by vintage year one	38,021	29,724
Term loans by vintage year two	18,865	18,253
Term loans by vintage year three	10,789	10,209
Term loans by vintage year four	5,487	6,191
Term loans by vintage year five	2,816	2,717
Term loans by vintage after year five	1,287	1,102
Total term loans	77,265	68,196
Revolving loans	373	683
Revolving loans converted to term	8	9
Total	77,646	68,888
Auto \| Consumer Banking
Financing Receivable, Credit Quality Indicator [Line Items]
Term loans by vintage year one	37,736	28,683
Term loans by vintage year two	18,687	18,020
Term loans by vintage year three	10,615	9,995
Term loans by vintage year four	5,318	5,967
Term loans by vintage year five	2,639	2,542
Term loans by vintage after year five	784	555
Total term loans	75,779	65,762
Revolving loans	0	0
Revolving loans converted to term	0	0
Total	75,779	65,762
Retail banking \| Consumer Banking
Financing Receivable, Credit Quality Indicator [Line Items]
Term loans by vintage year one	285	1,041
Term loans by vintage year two	178	233
Term loans by vintage year three	174	214
Term loans by vintage year four	169	224
Term loans by vintage year five	177	175
Term loans by vintage after year five	503	547
Total term loans	1,486	2,434
Revolving loans	373	683
Revolving loans converted to term	8	9
Total	1,867	3,126
PPP loans	232	919
Current \| Retail banking \| Consumer Banking
Financing Receivable, Credit Quality Indicator [Line Items]
Term loans by vintage year one	285	1,041
Term loans by vintage year two	171	233
Term loans by vintage year three	172	206
Term loans by vintage year four	161	222
Term loans by vintage year five	176	167
Term loans by vintage after year five	491	537
Total term loans	1,456	2,406
Revolving loans	345	651
Revolving loans converted to term	6	7
Total	1,807	3,064
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	2	0
Term loans by vintage year three	2	7
Term loans by vintage year four	7	1
Term loans by vintage year five	0	2
Term loans by vintage after year five	1	2
Total term loans	12	12
Revolving loans	23	15
Revolving loans converted to term	0	1
Total	35	28
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	4	0
Term loans by vintage year three	0	1
Term loans by vintage year four	0	0
Term loans by vintage year five	0	5
Term loans by vintage after year five	2	4
Total term loans	6	10
Revolving loans	1	8
Revolving loans converted to term	0	1
Total	7	19
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	1	0
Term loans by vintage year three	0	0
Term loans by vintage year four	1	1
Term loans by vintage year five	1	1
Term loans by vintage after year five	9	4
Total term loans	12	6
Revolving loans	4	9
Revolving loans converted to term	2	0
Total	18	15
Greater than 660 \| Auto \| Consumer Banking
Financing Receivable, Credit Quality Indicator [Line Items]
Term loans by vintage year one	20,758	13,352
Term loans by vintage year two	8,630	8,091
Term loans by vintage year three	4,739	4,675
Term loans by vintage year four	2,394	2,810
Term loans by vintage year five	1,153	1,168
Term loans by vintage after year five	301	203
Total term loans	37,975	30,299
Revolving loans	0	0
Revolving loans converted to term	0	0
Total	37,975	30,299
621-660 \| Auto \| Consumer Banking
Financing Receivable, Credit Quality Indicator [Line Items]
Term loans by vintage year one	7,456	5,781
Term loans by vintage year two	3,721	3,631
Term loans by vintage year three	2,109	2,003
Term loans by vintage year four	1,084	1,172
Term loans by vintage year five	537	488
Term loans by vintage after year five	157	109
Total term loans	15,064	13,184
Revolving loans	0	0
Revolving loans converted to term	0	0
Total	15,064	13,184
620 or below \| Auto \| Consumer Banking
Financing Receivable, Credit Quality Indicator [Line Items]
Term loans by vintage year one	9,522	9,550
Term loans by vintage year two	6,336	6,298
Term loans by vintage year three	3,767	3,317
Term loans by vintage year four	1,840	1,985
Term loans by vintage year five	949	886
Term loans by vintage after year five	326	243
Total term loans	22,740	22,279
Revolving loans	0	0
Revolving loans converted to term	0	0
Total	$ 22,740	$ 22,279

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