Loans - Consumer, Excluding Credit Card Loan Portfolio, Auto and Other (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025
Loans by origination year
Total retained loans	$ 1,425,236	$ 1,300,990	$ 1,408,905
Gross charge-offs by origination year
Total gross charge-offs	2,911	2,816
Consumer, excluding credit card
Loans by origination year
Total retained loans	367,274	372,892	368,741
Gross charge-offs by origination year
Total gross charge-offs	261	$ 287
Consumer, excluding credit card | Auto and other
Loans by origination year
Term loans originated in 2026/2025	7,807		26,660
Term loans originated in 2025/2024	23,896		15,768
Term loans originated in 2024/2023	14,077		9,670
Term loans originated in 2023/2022	8,324		5,069
Term loans originated in 2022/2021	4,214		3,061
Term loans originated prior to 2022/2021	2,885		871
Revolving loans within the revolving period	3,845		3,852
Revolving loans converted to term loans	279		259
Total retained loans	$ 65,327		$ 65,210
% 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 2026/2025	0.54%		0.64%
% of 30 plus days past due to total retained loans, Term loans originated in 2025/2024	0.65%		1.15%
% of 30 plus days past due to total retained loans, Term loans originated in 2024/2023	1.14%		2.35%
% of 30 plus days past due to total retained loans, Term loans originated in 2023/2022	2.22%		3.35%
% of 30 plus days past due to total retained loans, Term loans originated in 2022/2021	3.23%		3.23%
% of 30 plus days past due to total retained loans, Term loans originated prior to 2022/2021	3.05%		2.87%
% of 30 plus days past due to total retained loans, Revolving loans within the revolving period	0.86%		0.91%
% of 30 plus days past due to total retained loans, Revolving loans converted to term loans	32.62%		31.66%
% of 30 plus days past due to total retained loans	1.36%		1.52%
Gross charge-offs by origination year
Gross charge-offs originated in 2026/2025	$ 18		$ 242
Gross charge-offs originated in 2025/2024	78		228
Gross charge-offs originated in 2024/2023	48		244
Gross charge-offs originated in 2023/2022	50		157
Gross charge-offs originated in 2022/2021	27		69
Gross charge-offs originated prior to 2022/2021	29		83
Gross charge-offs originated within the revolving period	0		0
Gross charge-offs originated converted to term loans	2		8
Total gross charge-offs	252		1,031
Current | Consumer, excluding credit card | Auto and other
Loans by origination year
Term loans originated in 2026/2025	7,765		26,490
Term loans originated in 2025/2024	23,741		15,586
Term loans originated in 2024/2023	13,917		9,443
Term loans originated in 2023/2022	8,139		4,899
Term loans originated in 2022/2021	4,078		2,961
Term loans originated prior to 2022/2021	2,796		846
Revolving loans within the revolving period	3,812		3,817
Revolving loans converted to term loans	188		177
Total retained loans	64,436		64,219
30–119 days past due | Consumer, excluding credit card | Auto and other
Loans by origination year
Term loans originated in 2026/2025	42		170
Term loans originated in 2025/2024	155		180
Term loans originated in 2024/2023	158		225
Term loans originated in 2023/2022	184		170
Term loans originated in 2022/2021	136		99
Term loans originated prior to 2022/2021	88		25
Revolving loans within the revolving period	32		33
Revolving loans converted to term loans	52		48
Total retained loans	847		950
120 or more days past due | Consumer, excluding credit card | Auto and other
Loans by origination year
Term loans originated in 2026/2025	0		0
Term loans originated in 2025/2024	0		2
Term loans originated in 2024/2023	2		2
Term loans originated in 2023/2022	1		0
Term loans originated in 2022/2021	0		1
Term loans originated prior to 2022/2021	1		0
Revolving loans within the revolving period	1		2
Revolving loans converted to term loans	39		34
Total retained loans	$ 44		$ 41