Lending Activities - Credit quality of residential mortgages (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 50,321	$ 46,677
Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	997	2,956
Prior year	3,016	964
Two years prior	852	408
Three years prior	327	167
Four years prior	120	274
Five years & beyond prior	818	723
Total	6,130	5,492
780 and greater | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	296	1,601
Prior year	2,204	691
Two years prior	654	297
Three years prior	232	107
Four years prior	77	192
Five years & beyond prior	567	501
Total	4,030	3,389
720 - 779 | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	536	1,306
Prior year	728	230
Two years prior	168	86
Three years prior	76	44
Four years prior	32	58
Five years & beyond prior	169	154
Total	1,709	1,878
660 - 719 | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	163	48
Prior year	80	42
Two years prior	28	22
Three years prior	16	12
Four years prior	9	20
Five years & beyond prior	62	49
Total	358	193
600 - 659 | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	2	1
Prior year	4	1
Two years prior	2	2
Three years prior	2	3
Four years prior	2	2
Five years & beyond prior	14	12
Total	26	21
Less than 600 | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	0	0
Prior year	0	0
Two years prior	0	1
Three years prior	1	1
Four years prior	0	2
Five years & beyond prior	6	7
Total	$ 7	$ 11