Loans - Consumer, Excluding Credit Card Loan Portfolio, Residential Real Estate (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 | 30 or more days past due | U.S. government-guaranteed
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	32	31
Consumer, excluding credit card | Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans originated in 2022/2021	30,557	68,755
Term loans originated in 2021/2020	67,513	48,368
Term loans originated in 2020/2019	44,830	18,476
Term loans originated in 2019/2018	16,143	7,981
Term loans originated in 2018/2017	6,773	11,739
Term loans originated prior to 2018/2017	54,421	50,794
Revolving loans within the revolving period	5,920	6,409
Revolving loans converted to term loans	10,985	12,273
Total retained loans	$ 237,142	$ 224,795
% of 30 plus days past due to total retained loans, Term loans originated in 2022/2021	0.02%	0.02%
% of 30 plus days past due to total retained loans, Term loans originated in 2021/2020	0.03%	0.07%
% of 30 plus days past due to total retained loans, Term loans originated in 2020/2019	0.03%	0.26%
% of 30 plus days past due to total retained loans, Term loans originated in 2019/2018	0.15%	0.65%
% of 30 plus days past due to total retained loans, Term loans originated in 2018/2017	0.34%	0.47%
% of 30 plus days past due to total retained loans, Term loans originated prior to 2018/2017	2.11%	3.18%
% of 30 plus days past due to total retained loans, Revolving loans within the revolving period	0.24%	0.27%
% of 30 plus days past due to total retained loans, Revolving loans converted to term loans	3.36%	3.80%
% of 30 plus days past due to total retained loans	0.68%	1.02%
Consumer, excluding credit card | Residential real estate | Senior lien
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of total revolving loans that are senior lien loans	37.00%
Consumer, excluding credit card | Residential real estate | U.S. government-guaranteed
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 62	$ 66
Consumer, excluding credit card | Residential real estate | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans originated in 2022/2021	30,550	68,742
Term loans originated in 2021/2020	67,493	48,334
Term loans originated in 2020/2019	44,816	18,428
Term loans originated in 2019/2018	16,118	7,929
Term loans originated in 2018/2017	6,750	11,684
Term loans originated prior to 2018/2017	53,243	49,147
Revolving loans within the revolving period	5,906	6,392
Revolving loans converted to term loans	10,616	11,807
Total retained loans	235,492	222,463
Consumer, excluding credit card | Residential real estate | Current | U.S. government-guaranteed
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	30	35
Consumer, excluding credit card | Residential real estate | 30–149 days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans originated in 2022/2021	7	13
Term loans originated in 2021/2020	20	23
Term loans originated in 2020/2019	11	27
Term loans originated in 2019/2018	14	27
Term loans originated in 2018/2017	10	22
Term loans originated prior to 2018/2017	545	578
Revolving loans within the revolving period	9	11
Revolving loans converted to term loans	164	182
Total retained loans	780	883
Consumer, excluding credit card | Residential real estate | 30–149 days past due | U.S. government-guaranteed
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	11	11
Consumer, excluding credit card | Residential real estate | 150 or more days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans originated in 2022/2021	0	0
Term loans originated in 2021/2020	0	11
Term loans originated in 2020/2019	3	21
Term loans originated in 2019/2018	11	25
Term loans originated in 2018/2017	13	33
Term loans originated prior to 2018/2017	633	1,069
Revolving loans within the revolving period	5	6
Revolving loans converted to term loans	205	284
Total retained loans	870	1,449
Consumer, excluding credit card | Residential real estate | 150 or more days past due | U.S. government-guaranteed
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 21	$ 20