Lending Activities - Credit Quality of Commercial Mortgages (Details) - Commercial mortgages $ in Millions	Sep. 30, 2024 USD ($)	Dec. 31, 2023 USD ($)
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	$ 54	$ 403
Prior year	510	249
Two years prior	261	648
Three years prior	605	191
Four years prior	164	177
Five years & beyond prior	2,102	2,168
Total	$ 3,696	$ 3,836
Weighted average debt service coverage ratio	1.9	1.8
Weighted average loan-to-value ratio (as a percent)	64.00%	62.00%
Less than 65%
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	$ 34	$ 359
Prior year	411	159
Two years prior	169	492
Three years prior	493	177
Four years prior	156	156
Five years & beyond prior	1,368	1,385
Total	2,631	2,728
65% to 75%
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	13	10
Prior year	42	15
Two years prior	48	137
Three years prior	77	0
Four years prior	0	21
Five years & beyond prior	302	367
Total	482	550
76% to 80%
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	0	0
Prior year	0	32
Two years prior	0	10
Three years prior	35	0
Four years prior	0	0
Five years & beyond prior	113	0
Total	148	42
Greater than 80%
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	7	34
Prior year	57	43
Two years prior	44	9
Three years prior	0	14
Four years prior	8	0
Five years & beyond prior	319	416
Total	435	516
Greater than 1.2X
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	34	398
Prior year	500	167
Two years prior	246	394
Three years prior	559	135
Four years prior	164	156
Five years & beyond prior	1,766	1,784
Total	3,269	3,034
1.00 - 1.20X
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	20	5
Prior year	10	71
Two years prior	15	254
Three years prior	14	56
Four years prior	0	21
Five years & beyond prior	80	298
Total	139	705
Less than 1.00X
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	0	0
Prior year	0	11
Two years prior	0	0
Three years prior	32	0
Four years prior	0	0
Five years & beyond prior	256	86
Total	$ 288	$ 97