Loans - Consumer, Excluding Credit Card Loan Portfolio, Auto and Other (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021	Jun. 30, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 1,052,390	$ 1,010,206	$ 963,665
Consumer, excluding credit card
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	302,631	295,556	$ 297,731
Consumer, excluding credit card | Auto and other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans originated in 2022/2021	12,592	35,515
Term loans originated in 2021/2020	26,551	19,079
Term loans originated in 2020/2019	14,639	7,531
Term loans originated in 2019/2018	5,577	3,724
Term loans originated in 2018/2017	2,450	1,832
Term loans originated prior to 2018/2017	1,298	688
Revolving loans within the revolving period	2,256	2,259
Revolving loans converted to term loans	126	133
Total retained loans	$ 65,489	$ 70,761
% of 30 plus days past due to total retained loans, Term loans originated in 2022/2021	0.83%	0.54%
% of 30 plus days past due to total retained loans, Term loans originated in 2021/2020	0.72%	0.47%
% of 30 plus days past due to total retained loans, Term loans originated in 2020/2019	0.57%	1.17%
% of 30 plus days past due to total retained loans, Term loans originated in 2019/2018	1.26%	1.42%
% of 30 plus days past due to total retained loans, Term loans originated in 2018/2017	1.55%	1.75%
% of 30 plus days past due to total retained loans, Term loans originated prior to 2018/2017	2.23%	3.20%
% of 30 plus days past due to total retained loans, Revolving loans within the revolving period	0.66%	0.75%
% of 30 plus days past due to total retained loans, Revolving loans converted to term loans	7.94%	9.77%
% of 30 plus days past due to total retained loans	0.83%	0.71%
Consumer, excluding credit card | Auto and other | Paycheck Protection Program (PPP)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 1,500	$ 5,400
Current | Consumer, excluding credit card | Auto and other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans originated in 2022/2021	12,488	35,323
Term loans originated in 2021/2020	26,358	18,324
Term loans originated in 2020/2019	14,459	7,443
Term loans originated in 2019/2018	5,507	3,671
Term loans originated in 2018/2017	2,412	1,800
Term loans originated prior to 2018/2017	1,269	666
Revolving loans within the revolving period	2,241	2,242
Revolving loans converted to term loans	116	120
Total retained loans	64,850	69,589
Current | Consumer, excluding credit card | Auto and other | Paycheck Protection Program (PPP)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans originated in 2022/2021		4,400
Term loans originated in 2021/2020	1,300	1,000
Term loans originated in 2020/2019	197
30 or more days past due | Consumer, excluding credit card | Auto and other | Paycheck Protection Program (PPP)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	97	667
30–119 days past due | Consumer, excluding credit card | Auto and other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans originated in 2022/2021	104	192
Term loans originated in 2021/2020	193	720
Term loans originated in 2020/2019	99	88
Term loans originated in 2019/2018	69	53
Term loans originated in 2018/2017	38	31
Term loans originated prior to 2018/2017	28	21
Revolving loans within the revolving period	11	12
Revolving loans converted to term loans	5	6
Total retained loans	547	1,123
120 or more days past due | Consumer, excluding credit card | Auto and other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans originated in 2022/2021	0	0
Term loans originated in 2021/2020	0	35
Term loans originated in 2020/2019	81	0
Term loans originated in 2019/2018	1	0
Term loans originated in 2018/2017	0	1
Term loans originated prior to 2018/2017	1	1
Revolving loans within the revolving period	4	5
Revolving loans converted to term loans	5	7
Total retained loans	$ 92	$ 49