v3.26.3
Concentration of Credit and Other Risks - Concentration of Credit Risk - Multifamily Mortgage Portfolio (Details)(Details)
$ in Millions
Sep. 30, 2026
USD ($)
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 0.58%
Northeast  
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 0.87%
West  
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 0.33%
Southeast  
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 0.38%
Southwest  
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 0.88%
North Central  
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 0.31%
California  
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 0.24%
Texas  
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 0.99%
Florida  
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 0.31%
New York  
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 2.02%
Georgia  
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 0.22%
All Other  
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 0.43%
Geographic Concentration Risk | All Other  
Concentration Risk [Line Items]  
Portfolio UPB $ 1,972,001
Unpaid Principal Balance, Percent Of Portfolio 62.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member]  
Concentration Risk [Line Items]  
Portfolio UPB $ 509,584
Unpaid Principal Balance, Percent Of Portfolio 100.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member] | Northeast  
Concentration Risk [Line Items]  
Portfolio UPB $ 130,076
Unpaid Principal Balance, Percent Of Portfolio 26.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member] | West  
Concentration Risk [Line Items]  
Portfolio UPB $ 117,673
Unpaid Principal Balance, Percent Of Portfolio 23.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member] | Southeast  
Concentration Risk [Line Items]  
Portfolio UPB $ 108,848
Unpaid Principal Balance, Percent Of Portfolio 21.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member] | Southwest  
Concentration Risk [Line Items]  
Portfolio UPB $ 97,919
Unpaid Principal Balance, Percent Of Portfolio 19.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member] | North Central  
Concentration Risk [Line Items]  
Portfolio UPB $ 55,068
Unpaid Principal Balance, Percent Of Portfolio 11.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member] | California  
Concentration Risk [Line Items]  
Portfolio UPB $ 64,567
Unpaid Principal Balance, Percent Of Portfolio 13.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member] | Texas  
Concentration Risk [Line Items]  
Portfolio UPB $ 61,101
Unpaid Principal Balance, Percent Of Portfolio 12.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member] | Florida  
Concentration Risk [Line Items]  
Portfolio UPB $ 46,708
Unpaid Principal Balance, Percent Of Portfolio 9.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member] | New York  
Concentration Risk [Line Items]  
Portfolio UPB $ 40,782
Unpaid Principal Balance, Percent Of Portfolio 8.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member] | Georgia  
Concentration Risk [Line Items]  
Portfolio UPB $ 22,301
Unpaid Principal Balance, Percent Of Portfolio 4.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member] | All Other  
Concentration Risk [Line Items]  
Portfolio UPB $ 274,125
Unpaid Principal Balance, Percent Of Portfolio 54.00%