v3.25.3
Concentration of Credit and Other Risks - Concentration of Credit Risk - Multifamily Mortgage Portfolio (Details)(Details)
$ in Millions
Sep. 30, 2025
USD ($)
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 0.51%
Northeast  
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 0.91%
West  
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 0.21%
Southeast  
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 0.14%
Southwest  
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 0.58%
North Central  
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 0.79%
California  
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 0.33%
Texas  
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 0.54%
Florida  
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 0.13%
New York  
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 2.23%
Georgia  
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 0.22%
All Other  
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 0.37%
Geographic Concentration Risk | All Other  
Concentration Risk [Line Items]  
Portfolio UPB $ 1,934,235
Unpaid Principal Balance, Percent Of Portfolio 62.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member]  
Concentration Risk [Line Items]  
Portfolio UPB $ 479,964
Unpaid Principal Balance, Percent Of Portfolio 100.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member] | Northeast  
Concentration Risk [Line Items]  
Portfolio UPB $ 121,413
Unpaid Principal Balance, Percent Of Portfolio 25.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member] | West  
Concentration Risk [Line Items]  
Portfolio UPB $ 113,995
Unpaid Principal Balance, Percent Of Portfolio 24.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member] | Southeast  
Concentration Risk [Line Items]  
Portfolio UPB $ 99,082
Unpaid Principal Balance, Percent Of Portfolio 21.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member] | Southwest  
Concentration Risk [Line Items]  
Portfolio UPB $ 95,813
Unpaid Principal Balance, Percent Of Portfolio 20.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member] | North Central  
Concentration Risk [Line Items]  
Portfolio UPB $ 49,661
Unpaid Principal Balance, Percent Of Portfolio 10.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member] | California  
Concentration Risk [Line Items]  
Portfolio UPB $ 61,303
Unpaid Principal Balance, Percent Of Portfolio 13.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member] | Texas  
Concentration Risk [Line Items]  
Portfolio UPB $ 60,245
Unpaid Principal Balance, Percent Of Portfolio 13.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member] | Florida  
Concentration Risk [Line Items]  
Portfolio UPB $ 42,141
Unpaid Principal Balance, Percent Of Portfolio 9.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member] | New York  
Concentration Risk [Line Items]  
Portfolio UPB $ 38,682
Unpaid Principal Balance, Percent Of Portfolio 8.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member] | Georgia  
Concentration Risk [Line Items]  
Portfolio UPB $ 20,349
Unpaid Principal Balance, Percent Of Portfolio 4.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member] | All Other  
Concentration Risk [Line Items]  
Portfolio UPB $ 257,244
Unpaid Principal Balance, Percent Of Portfolio 53.00%