Lending Activities - Credit Quality of Residential Mortgages (Details) - Residential mortgages - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	$ 322	$ 1,950
Prior year	2,211	1,492
Two years prior	1,417	2,969
Three years prior	2,996	841
Four years prior	849	389
Five years & beyond prior	1,446	1,048
Total	9,241	8,689
Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Total	2,300	1,700
780 and greater
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	55	514
Prior year	699	589
Two years prior	594	2,283
Three years prior	2,295	622
Four years prior	643	240
Five years & beyond prior	845	608
Total	5,131	4,856
720 - 779
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	198	1,121
Prior year	1,134	625
Two years prior	539	560
Three years prior	543	169
Four years prior	151	99
Five years & beyond prior	345	243
Total	2,910	2,817
660 - 719
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	69	313
Prior year	364	257
Two years prior	232	113
Three years prior	131	40
Four years prior	40	37
Five years & beyond prior	168	128
Total	1,004	888
600 - 659
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	0	2
Prior year	12	20
Two years prior	34	11
Three years prior	18	8
Four years prior	10	9
Five years & beyond prior	59	53
Total	133	103
Less than 600
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	0	0
Prior year	2	1
Two years prior	18	2
Three years prior	9	2
Four years prior	5	4
Five years & beyond prior	29	16
Total	$ 63	$ 25