Lending Activities - Credit quality of residential mortgages (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 52,411	$ 50,321
Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	1,121	997
Prior year	1,406	3,016
Two years prior	2,953	852
Three years prior	855	327
Four years prior	355	120
Five years & beyond prior	1,018	818
Total	7,708	6,130
780 and greater | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	285	296
Prior year	553	2,204
Two years prior	2,317	654
Three years prior	640	232
Four years prior	241	77
Five years & beyond prior	628	567
Total	4,664	4,030
720 - 779 | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	664	536
Prior year	582	728
Two years prior	540	168
Three years prior	169	76
Four years prior	80	32
Five years & beyond prior	235	169
Total	2,270	1,709
660 - 719 | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	170	163
Prior year	250	80
Two years prior	88	28
Three years prior	38	16
Four years prior	26	9
Five years & beyond prior	106	62
Total	678	358
600 - 659 | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	2	2
Prior year	21	4
Two years prior	7	2
Three years prior	7	2
Four years prior	6	2
Five years & beyond prior	40	14
Total	83	26
Less than 600 | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	0	0
Prior year	0	0
Two years prior	1	0
Three years prior	1	1
Four years prior	2	0
Five years & beyond prior	9	6
Total	$ 13	$ 7