Mortgage Loans - Credit Quality Indicators - MF (Details) - Multifamily - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	$ 6,042	$ 50,494
One fiscal year before	54,464	60,908
Two fiscal years before	60,689	64,398
Three fiscal years before	64,291	75,526
Four fiscal years before	75,317	60,850
Prior	207,041	149,178
Total mortgage loans	467,844	461,354
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	6,042	49,944
One fiscal year before	53,999	51,380
Two fiscal years before	51,313	60,563
Three fiscal years before	60,426	72,791
Four fiscal years before	72,831	56,901
Prior	191,517	136,860
Total mortgage loans	436,128	428,439
Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	4
One fiscal year before	4	11
Two fiscal years before	11	181
Three fiscal years before	245	32
Four fiscal years before	22	46
Prior	135	130
Total mortgage loans	417	404
Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	521
One fiscal year before	461	9,517
Two fiscal years before	9,365	3,654
Three fiscal years before	3,620	2,703
Four fiscal years before	2,464	3,893
Prior	15,388	12,188
Total mortgage loans	31,298	32,476
Substandard | Senior Housing
Financing Receivable, Credit Quality Indicator [Line Items]
Total mortgage loans	6,700	6,900
Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	25
One fiscal year before	0	0
Two fiscal years before	0	0
Three fiscal years before	0	0
Four fiscal years before	0	10
Prior	1	0
Total mortgage loans	1	35
Current-year write-offs
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
One fiscal year before	29	3
Two fiscal years before	4	4
Three fiscal years before	9	6
Four fiscal years before	13	23
Prior	78	365
Total mortgage loans	$ 133	$ 401