Mortgage Loans - Credit Quality Indicators - MF (Details) - Multifamily - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	$ 42,455	$ 50,350
One fiscal year before	54,622	53,930
Two fiscal years before	53,269	58,780
Three fiscal years before	56,991	63,361
Four fiscal years before	62,119	74,319
Prior	241,494	188,987
Total mortgage loans	510,950	489,727
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	42,455	49,867
One fiscal year before	53,537	51,194
Two fiscal years before	49,962	49,570
Three fiscal years before	49,035	59,687
Four fiscal years before	58,886	71,657
Prior	228,139	175,887
Total mortgage loans	482,014	457,862
Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	54
One fiscal year before	57	68
Two fiscal years before	68	165
Three fiscal years before	192	353
Four fiscal years before	347	162
Prior	604	280
Total mortgage loans	1,268	1,082
Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	429
One fiscal year before	1,028	2,626
Two fiscal years before	3,239	9,045
Three fiscal years before	7,725	3,259
Four fiscal years before	2,886	2,500
Prior	12,750	12,820
Total mortgage loans	27,628	30,679
Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
One fiscal year before	0	42
Two fiscal years before	0	0
Three fiscal years before	39	62
Four fiscal years before	0	0
Prior	1	0
Total mortgage loans	40	104
Current-year write-offs
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
One fiscal year before	5	81
Two fiscal years before	92	192
Three fiscal years before	76	16
Four fiscal years before	52	27
Prior	125	189
Total mortgage loans	$ 350	$ 505