Concentration of Credit and Other Risks - Concentration of Credit Risk - Multifamily Mortgage Portfolio (Details) $ in Millions	Dec. 31, 2025 USD ($)
Concentration Risk [Line Items]
Multifamily Delinquency Rate	0.44%
Northeast [Member]
Concentration Risk [Line Items]
Multifamily Delinquency Rate	0.81%
West [Member]
Concentration Risk [Line Items]
Multifamily Delinquency Rate	0.19%
Southeast [Member]
Concentration Risk [Line Items]
Multifamily Delinquency Rate	0.16%
Southwest [Member]
Concentration Risk [Line Items]
Multifamily Delinquency Rate	0.59%
North Central [Member]
Concentration Risk [Line Items]
Multifamily Delinquency Rate	0.40%
CALIFORNIA
Concentration Risk [Line Items]
Multifamily Delinquency Rate	0.30%
TEXAS
Concentration Risk [Line Items]
Multifamily Delinquency Rate	0.53%
FLORIDA
Concentration Risk [Line Items]
Multifamily Delinquency Rate	0.10%
NEW YORK
Concentration Risk [Line Items]
Multifamily Delinquency Rate	2.05%
GEORGIA
Concentration Risk [Line Items]
Multifamily Delinquency Rate	0.06%
All Other
Concentration Risk [Line Items]
Multifamily Delinquency Rate	0.30%
All Other | Geographic Concentration Risk
Concentration Risk [Line Items]
Concentration risk, unpaid principal balance	$ 1,946,619
Unpaid principal balance, percent of portfolio	62.00%
Multifamily Unpaid Principal Balance | Geographic Concentration Risk
Concentration Risk [Line Items]
Concentration risk, unpaid principal balance	$ 495,835
Unpaid principal balance, percent of portfolio	100.00%
Multifamily Unpaid Principal Balance | Northeast [Member] | Geographic Concentration Risk
Concentration Risk [Line Items]
Concentration risk, unpaid principal balance	$ 126,400
Unpaid principal balance, percent of portfolio	25.00%
Multifamily Unpaid Principal Balance | West [Member] | Geographic Concentration Risk
Concentration Risk [Line Items]
Concentration risk, unpaid principal balance	$ 116,239
Unpaid principal balance, percent of portfolio	23.00%
Multifamily Unpaid Principal Balance | Southeast [Member] | Geographic Concentration Risk
Concentration Risk [Line Items]
Concentration risk, unpaid principal balance	$ 104,266
Unpaid principal balance, percent of portfolio	21.00%
Multifamily Unpaid Principal Balance | Southwest [Member] | Geographic Concentration Risk
Concentration Risk [Line Items]
Concentration risk, unpaid principal balance	$ 96,952
Unpaid principal balance, percent of portfolio	20.00%
Multifamily Unpaid Principal Balance | North Central [Member] | Geographic Concentration Risk
Concentration Risk [Line Items]
Concentration risk, unpaid principal balance	$ 51,978
Unpaid principal balance, percent of portfolio	11.00%
Multifamily Unpaid Principal Balance | CALIFORNIA | Geographic Concentration Risk
Concentration Risk [Line Items]
Concentration risk, unpaid principal balance	$ 62,128
Unpaid principal balance, percent of portfolio	13.00%
Multifamily Unpaid Principal Balance | TEXAS | Geographic Concentration Risk
Concentration Risk [Line Items]
Concentration risk, unpaid principal balance	$ 60,963
Unpaid principal balance, percent of portfolio	12.00%
Multifamily Unpaid Principal Balance | FLORIDA | Geographic Concentration Risk
Concentration Risk [Line Items]
Concentration risk, unpaid principal balance	$ 45,235
Unpaid principal balance, percent of portfolio	9.00%
Multifamily Unpaid Principal Balance | NEW YORK | Geographic Concentration Risk
Concentration Risk [Line Items]
Concentration risk, unpaid principal balance	$ 39,404
Unpaid principal balance, percent of portfolio	8.00%
Multifamily Unpaid Principal Balance | GEORGIA | Geographic Concentration Risk
Concentration Risk [Line Items]
Concentration risk, unpaid principal balance	$ 21,266
Unpaid principal balance, percent of portfolio	4.00%
Multifamily Unpaid Principal Balance | All Other | Geographic Concentration Risk
Concentration Risk [Line Items]
Concentration risk, unpaid principal balance	$ 266,839
Unpaid principal balance, percent of portfolio	54.00%