v3.26.3
Advances (Details) - Table - Concentration Risk - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Dec. 31, 2025
Percent of Interest Income from Advances          
Federal Home Loan Bank, Advance, Branch of FHLBank, Amount $ 30,961   $ 30,961   $ 38,149
Concentration Risk [Line Items]          
Federal Home Loan Bank, Advance, Branch of FHLBank, Amount 30,961   30,961   $ 38,149
Top Ten Borrowers | Western Alliance Bank          
Percent of Interest Income from Advances          
Federal Home Loan Bank, Advance, Branch of FHLBank, Amount 5,200 $ 3,400 5,200 $ 3,400  
Concentration Risk [Line Items]          
Federal Home Loan Bank, Advance, Branch of FHLBank, Amount 5,200 3,400 5,200 3,400  
Interest Income from Advances $ 34 $ 48 $ 100 $ 145  
Top Ten Borrowers | Percentage of Total Advances Outstanding | Western Alliance Bank          
Percent of Interest Income from Advances          
Percentage of Total Capital Stock Outstanding     17.00% 10.00%  
Concentration Risk [Line Items]          
Percentage of Total Capital Stock Outstanding     17.00% 10.00%  
Top Ten Borrowers | Percentage of Total Interest Income from Advances | Western Alliance Bank          
Percent of Interest Income from Advances          
Percentage of Total Capital Stock Outstanding 10.00% 11.00% 9.00% 11.00%  
Concentration Risk [Line Items]          
Percentage of Total Capital Stock Outstanding 10.00% 11.00% 9.00% 11.00%