v3.26.1
Concentration of Credit and Other Risks - Concentration of Credit Risk - Multifamily Mortgage Portfolio (Details)(Details)
$ in Millions
Mar. 31, 2026
USD ($)
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 0.43%
Northeast  
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 0.87%
West  
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 0.21%
Southeast  
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 0.10%
Southwest  
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 0.52%
North Central  
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 0.35%
California  
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 0.31%
Texas  
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 0.48%
Florida  
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 0.10%
New York  
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 2.10%
Georgia  
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 0.06%
All Other  
Concentration Risk [Line Items]  
Multifamily Delinquency Rate 0.28%
Geographic Concentration Risk | All Other  
Concentration Risk [Line Items]  
Portfolio UPB $ 1,949,629
Unpaid Principal Balance, Percent Of Portfolio 62.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member]  
Concentration Risk [Line Items]  
Portfolio UPB $ 498,332
Unpaid Principal Balance, Percent Of Portfolio 100.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member] | Northeast  
Concentration Risk [Line Items]  
Portfolio UPB $ 128,093
Unpaid Principal Balance, Percent Of Portfolio 26.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member] | West  
Concentration Risk [Line Items]  
Portfolio UPB $ 115,386
Unpaid Principal Balance, Percent Of Portfolio 23.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member] | Southeast  
Concentration Risk [Line Items]  
Portfolio UPB $ 105,307
Unpaid Principal Balance, Percent Of Portfolio 21.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member] | Southwest  
Concentration Risk [Line Items]  
Portfolio UPB $ 96,813
Unpaid Principal Balance, Percent Of Portfolio 19.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member] | North Central  
Concentration Risk [Line Items]  
Portfolio UPB $ 52,733
Unpaid Principal Balance, Percent Of Portfolio 11.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member] | California  
Concentration Risk [Line Items]  
Portfolio UPB $ 61,347
Unpaid Principal Balance, Percent Of Portfolio 12.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member] | Texas  
Concentration Risk [Line Items]  
Portfolio UPB $ 60,929
Unpaid Principal Balance, Percent Of Portfolio 12.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member] | Florida  
Concentration Risk [Line Items]  
Portfolio UPB $ 45,405
Unpaid Principal Balance, Percent Of Portfolio 9.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member] | New York  
Concentration Risk [Line Items]  
Portfolio UPB $ 39,756
Unpaid Principal Balance, Percent Of Portfolio 8.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member] | Georgia  
Concentration Risk [Line Items]  
Portfolio UPB $ 21,746
Unpaid Principal Balance, Percent Of Portfolio 4.00%
Geographic Concentration Risk | Multifamily Unpaid Principal Balance [Member] | All Other  
Concentration Risk [Line Items]  
Portfolio UPB $ 269,149
Unpaid Principal Balance, Percent Of Portfolio 55.00%