Loans - Consumer, Excluding Credit Card Loan Portfolio, Residential Real Estate (Details) - USD ($) $ in Millions	6 Months Ended		12 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Loans by origination year
Total retained loans	$ 1,273,047	$ 1,255,688	$ 1,280,870
Gross charge-offs by origination year
Total gross charge-offs	5,107	3,227
Consumer, excluding credit card
Loans by origination year
Total retained loans	382,795	396,195	397,275
Gross charge-offs by origination year
Total gross charge-offs	661	$ 501
Consumer, excluding credit card | Residential real estate
Loans by origination year
Term loans originated in 2024/2023	5,234		23,250
Term loans originated in 2023/2022	18,612		64,450
Term loans originated in 2022/2021	62,927		84,602
Term loans originated in 2021/2020	82,301		55,624
Term loans originated in 2020/2019	53,997		21,592
Term loans originated prior to 2020/2019	76,780		60,820
Revolving loans within the revolving period	7,046		7,533
Revolving loans converted to term loans	7,946		8,538
Total retained loans	$ 314,843		$ 326,409
% 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 2024/2023	0.59%		0.15%
% of 30 plus days past due to total retained loans, Term loans originated in 2022/2022	0.14%		0.13%
% of 30 plus days past due to total retained loans, Term loans originated in 2022/2021	0.29%		0.13%
% of 30 plus days past due to total retained loans, Term loans originated in 2021/2020	0.16%		0.14%
% of 30 plus days past due to total retained loans, Term loans originated in 2020/2019	0.15%		0.29%
% of 30 plus days past due to total retained loans, Term loans originated prior to 2020/2019	1.61%		2.04%
% of 30 plus days past due to total retained loans, Revolving loans within the revolving period	0.64%		0.72%
% of 30 plus days past due to total retained loans, Revolving loans converted to term loans	4.47%		4.53%
% of 30 plus days past due to total retained loans	0.66%		0.63%
Gross charge-offs by origination year
Gross charge-offs originated in 2024/2023	$ 0		$ 0
Gross charge-offs originated in 2023/2022	0		0
Gross charge-offs originated in 2022/2021	1		0
Gross charge-offs originated in 2021/2020	1		0
Gross charge-offs originated in 2020/2019	0		4
Gross charge-offs originated prior to 2020/2019	123		167
Gross charge-offs originated within the revolving period	10		26
Gross charge-offs originated converted to term loans	4		7
Total gross charge-offs	$ 139		204
Consumer, excluding credit card | Residential real estate | Senior lien
Gross charge-offs by origination year
Percentage of total revolving loans that are senior lien loans	37.00%
Consumer, excluding credit card | Residential real estate | Current
Loans by origination year
Term loans originated in 2024/2023	$ 5,203		23,216
Term loans originated in 2023/2022	18,586		64,366
Term loans originated in 2022/2021	62,746		84,496
Term loans originated in 2021/2020	82,170		55,546
Term loans originated in 2020/2019	53,916		21,530
Term loans originated prior to 2020/2019	75,532		59,563
Revolving loans within the revolving period	7,001		7,479
Revolving loans converted to term loans	7,591		8,151
Total retained loans	312,745		324,347
Consumer, excluding credit card | Residential real estate | 30–149 days past due
Loans by origination year
Term loans originated in 2024/2023	18		33
Term loans originated in 2023/2022	24		74
Term loans originated in 2022/2021	141		89
Term loans originated in 2021/2020	95		70
Term loans originated in 2020/2019	43		41
Term loans originated prior to 2020/2019	745		801
Revolving loans within the revolving period	18		49
Revolving loans converted to term loans	218		223
Total retained loans	1,302		1,380
Consumer, excluding credit card | Residential real estate | 150 or more days past due
Loans by origination year
Term loans originated in 2024/2023	13		1
Term loans originated in 2023/2022	2		10
Term loans originated in 2022/2021	40		17
Term loans originated in 2021/2020	36		8
Term loans originated in 2020/2019	38		21
Term loans originated prior to 2020/2019	503		456
Revolving loans within the revolving period	27		5
Revolving loans converted to term loans	137		164
Total retained loans	$ 796		$ 682