Loans - Consumer, Excluding Credit Card Loan Portfolio, Auto and Other (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Loans by origination year
Total retained loans	$ 1,280,870	$ 1,089,598	$ 1,010,206
Gross charge-offs by origination year
Total gross charge-offs	7,653	4,326	4,564
Consumer, excluding credit card
Loans by origination year
Total retained loans	397,275	300,753	295,556
Gross charge-offs by origination year
Total gross charge-offs	1,151	812	$ 630
Consumer, excluding credit card | Auto and other
Loans by origination year
Term loans originated in 2023/2022	30,605	22,450
Term loans originated in 2022/2021	15,077	20,573
Term loans originated in 2021/2020	13,063	11,525
Term loans originated in 2020/2019	6,624	4,059
Term loans originated in 2019/2018	1,820	1,500
Term loans originated prior to 2019/2018	528	596
Revolving loans within revolving period	3,006	2,356
Revolving loans converted to term loans	143	133
Total retained loans	$ 70,866	$ 63,192
% of 30+ days past due to total retained loans by origination year
% of 30 plus days past due to total retained loans, Term loans originated in 2023/2022	0.91%	1.17%
% of 30 plus days past due to total retained loans, Term loans originated in 2022/2021	1.86%	1.15%
% of 30 plus days past due to total retained loans, Term loans originated in 2021/2020	1.75%	0.83%
% of 30 plus days past due to total retained loans, Term loans originated in 2020/2019	1.15%	1.68%
% of 30 plus days past due to total retained loans, Term loans originated in 2019/2018	2.36%	2.20%
% of 30 plus days past due to total retained loans, Term loans originated prior to 2019/2018	3.22%	3.02%
% of 30 plus days past due to total retained loans, Revolving loans within the revolving period	0.73%	0.59%
% of 30 plus days past due to total retained loans, Revolving loans converted to term loans	28.67%	11.28%
% of 30 plus days past due to total retained loans	1.39%	1.18%
Gross charge-offs by origination year
Gross charge-offs originated in 2023	$ 333
Gross charge-offs originated in 2022	297
Gross charge-offs originated in 2021	161
Gross charge-offs originated in 2020	53
Gross charge-offs originated in 2019	35
Gross charge-offs originated prior to 2019	64
Gross charge-offs originated within the revolving period	0
Gross charge-offs originated converted to term loans	4
Total gross charge-offs	947
Consumer, excluding credit card | Auto and other | Current
Loans by origination year
Term loans originated in 2023/2022	30,328	$ 22,187
Term loans originated in 2022/2021	14,797	20,212
Term loans originated in 2021/2020	12,825	11,401
Term loans originated in 2020/2019	6,538	3,991
Term loans originated in 2019/2018	1,777	1,467
Term loans originated prior to 2019/2018	511	578
Revolving loans within revolving period	2,984	2,342
Revolving loans converted to term loans	102	118
Total retained loans	69,862	62,296
Consumer, excluding credit card | Auto and other | 30 or more days past due | Paycheck Protection Program (PPP)
Loans by origination year
Total retained loans	20	153
Consumer, excluding credit card | Auto and other | 30–119 days past due
Loans by origination year
Term loans originated in 2023/2022	276	263
Term loans originated in 2022/2021	279	308
Term loans originated in 2021/2020	231	100
Term loans originated in 2020/2019	78	68
Term loans originated in 2019/2018	43	33
Term loans originated prior to 2019/2018	17	17
Revolving loans within revolving period	19	12
Revolving loans converted to term loans	24	10
Total retained loans	967	811
Consumer, excluding credit card | Auto and other | 120 or more days past due
Loans by origination year
Term loans originated in 2023/2022	1	0
Term loans originated in 2022/2021	1	53
Term loans originated in 2021/2020	7	24
Term loans originated in 2020/2019	8	0
Term loans originated in 2019/2018	0	0
Term loans originated prior to 2019/2018	0	1
Revolving loans within revolving period	3	2
Revolving loans converted to term loans	17	5
Total retained loans	$ 37	$ 85