Lending Activities - Credit Quality of Commercial Mortgages (Details) - Commercial mortgages $ in Millions	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	$ 749	$ 2,850
Prior year	2,808	7,408
Two years prior	7,569	3,923
Three years prior	4,105	1,756
Four years prior	1,780	5,146
Five years & beyond prior	21,467	16,926
Total	$ 38,478	$ 38,009
Weighted average debt service coverage ratio	1.9	1.9
Weighted average loan-to-value ratio (as a percent)	60.00%	60.00%
Less than 65%
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	$ 749	$ 2,446
Prior year	2,520	4,629
Two years prior	4,716	2,741
Three years prior	2,858	1,303
Four years prior	1,329	2,832
Five years & beyond prior	13,730	11,571
Total	25,902	25,522
65% to 75%
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	0	290
Prior year	288	1,763
Two years prior	2,225	794
Three years prior	798	288
Four years prior	286	1,937
Five years & beyond prior	5,204	3,220
Total	8,801	8,292
76% to 80%
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	0	0
Prior year	0	375
Two years prior	0	99
Three years prior	99	0
Four years prior	0	377
Five years & beyond prior	836	340
Total	935	1,191
Greater than 80%
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	0	114
Prior year	0	641
Two years prior	628	289
Three years prior	350	165
Four years prior	165	0
Five years & beyond prior	1,697	1,795
Total	2,840	3,004
Greater than 1.2X
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	659	2,555
Prior year	2,388	6,209
Two years prior	6,371	2,349
Three years prior	2,577	1,387
Four years prior	1,412	4,969
Five years & beyond prior	17,872	13,459
Total	31,279	30,928
1.00 - 1.20X
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	90	295
Prior year	420	1,149
Two years prior	1,148	1,574
Three years prior	1,528	369
Four years prior	368	177
Five years & beyond prior	2,773	2,632
Total	6,327	6,196
Less than 1.00X
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	0	0
Prior year	0	50
Two years prior	50	0
Three years prior	0	0
Four years prior	0	0
Five years & beyond prior	822	835
Total	$ 872	$ 885