v3.26.1
Allowance for Losses on Loans - Schedule of Loans Based on Credit Quality Indicators (Details) - USD ($)
$ in Thousands
6 Months Ended 12 Months Ended
Mar. 31, 2026
Sep. 30, 2025
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans $ 20,168,933 $ 20,288,338
Pass    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans $ 18,988,971 $ 19,406,000
Pass | Accounts Receivable | Credit Concentration Risk    
Financing Receivable, Credit Quality Indicator [Line Items]    
Total grade as a % of total loans 94.10% 95.70%
Watch    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans $ 332,714  
Watch | Accounts Receivable | Credit Concentration Risk    
Financing Receivable, Credit Quality Indicator [Line Items]    
Total grade as a % of total loans 1.60%  
Special Mention    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans $ 328,345 $ 247,830
Special Mention | Accounts Receivable | Credit Concentration Risk    
Financing Receivable, Credit Quality Indicator [Line Items]    
Total grade as a % of total loans 1.60% 1.20%
Substandard    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans $ 516,496 $ 629,353
Substandard | Accounts Receivable | Credit Concentration Risk    
Financing Receivable, Credit Quality Indicator [Line Items]    
Total grade as a % of total loans 2.60% 3.10%
Doubtful    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans $ 2,407 $ 5,131
Doubtful | Accounts Receivable | Credit Concentration Risk    
Financing Receivable, Credit Quality Indicator [Line Items]    
Total grade as a % of total loans 0.00% 0.00%
Loss    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans   $ 24
Loss | Accounts Receivable | Credit Concentration Risk    
Financing Receivable, Credit Quality Indicator [Line Items]    
Total grade as a % of total loans   0.00%
Commercial loans    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans $ 12,241,938 $ 11,851,657
Commercial loans | Pass    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 11,091,994 10,994,504
Commercial loans | Watch    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 332,714  
Commercial loans | Special Mention    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 328,345 247,830
Commercial loans | Substandard    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 486,478 604,168
Commercial loans | Doubtful    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 2,407 5,131
Commercial loans | Loss    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans   24
Commercial loans | Multi-family    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 4,672,599 4,631,321
Commercial loans | Multi-family | Pass    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 4,178,496 4,337,347
Commercial loans | Multi-family | Watch    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 153,077  
Commercial loans | Multi-family | Special Mention    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 183,855 136,817
Commercial loans | Multi-family | Substandard    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 154,764 154,807
Commercial loans | Multi-family | Doubtful    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 2,407 2,350
Commercial loans | Multi-family | Loss    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans   0
Commercial loans | Commercial real estate    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 3,652,683 3,588,950
Commercial loans | Commercial real estate | Pass    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 3,432,409 3,339,062
Commercial loans | Commercial real estate | Watch    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 46,536  
Commercial loans | Commercial real estate | Special Mention    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 50,132 61,580
Commercial loans | Commercial real estate | Substandard    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 123,606 185,527
Commercial loans | Commercial real estate | Doubtful    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 0 2,781
Commercial loans | Commercial real estate | Loss    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans   0
Commercial loans | Commercial & industrial    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 2,791,133 2,386,363
Commercial loans | Commercial & industrial | Pass    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 2,437,792 2,086,750
Commercial loans | Commercial & industrial | Watch    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 113,386  
Commercial loans | Commercial & industrial | Special Mention    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 37,460 44,998
Commercial loans | Commercial & industrial | Substandard    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 202,495 254,591
Commercial loans | Commercial & industrial | Doubtful    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 0 0
Commercial loans | Commercial & industrial | Loss    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans   24
Commercial loans | Construction    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 956,957 1,105,101
Commercial loans | Construction | Pass    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 884,657 1,091,682
Commercial loans | Construction | Watch    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 10,014  
Commercial loans | Construction | Special Mention    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 56,898 4,435
Commercial loans | Construction | Substandard    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 5,388 8,984
Commercial loans | Construction | Doubtful    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 0 0
Commercial loans | Construction | Loss    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans   0
Commercial loans | Land - acquisition & development    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 168,566 139,922
Commercial loans | Land - acquisition & development | Pass    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 158,640 139,663
Commercial loans | Land - acquisition & development | Watch    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 9,701  
Commercial loans | Land - acquisition & development | Special Mention    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 0 0
Commercial loans | Land - acquisition & development | Substandard    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 225 259
Commercial loans | Land - acquisition & development | Doubtful    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 0 0
Commercial loans | Land - acquisition & development | Loss    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans   0
Consumer loans    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 7,926,995 8,436,681
Consumer loans | Pass    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 7,896,977 8,411,496
Consumer loans | Watch    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 0  
Consumer loans | Special Mention    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 0 0
Consumer loans | Substandard    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 30,018 25,185
Consumer loans | Doubtful    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 0 0
Consumer loans | Loss    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans   0
Consumer loans | Construction    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 38,867 78,243
Consumer loans | Construction | Pass    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 38,107 77,483
Consumer loans | Construction | Watch    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans  
Consumer loans | Construction | Special Mention    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 0 0
Consumer loans | Construction | Substandard    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 760 760
Consumer loans | Construction | Doubtful    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 0 0
Consumer loans | Construction | Loss    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans   0
Consumer loans | Single-family residential    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 7,501,331 7,936,931
Consumer loans | Single-family residential | Pass    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 7,473,143 7,913,120
Consumer loans | Single-family residential | Watch    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 0  
Consumer loans | Single-family residential | Special Mention    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 0 0
Consumer loans | Single-family residential | Substandard    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 28,188 23,811
Consumer loans | Single-family residential | Doubtful    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 0 0
Consumer loans | Single-family residential | Loss    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans   0
Consumer loans | Land - consumer lot loans    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 76,763 88,696
Consumer loans | Land - consumer lot loans | Pass    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 76,438 88,613
Consumer loans | Land - consumer lot loans | Watch    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans  
Consumer loans | Land - consumer lot loans | Special Mention    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 0 0
Consumer loans | Land - consumer lot loans | Substandard    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 325 83
Consumer loans | Land - consumer lot loans | Doubtful    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 0 0
Consumer loans | Land - consumer lot loans | Loss    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans   0
Consumer loans | HELOC    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 255,352 271,286
Consumer loans | HELOC | Pass    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 254,806 270,874
Consumer loans | HELOC | Watch    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans  
Consumer loans | HELOC | Special Mention    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 0 0
Consumer loans | HELOC | Substandard    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 546 412
Consumer loans | HELOC | Doubtful    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 0 0
Consumer loans | HELOC | Loss    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans   0
Consumer loans | Consumer    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 54,682 61,525
Consumer loans | Consumer | Pass    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 54,483 61,406
Consumer loans | Consumer | Watch    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans  
Consumer loans | Consumer | Special Mention    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 0 0
Consumer loans | Consumer | Substandard    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 199 119
Consumer loans | Consumer | Doubtful    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans $ 0 0
Consumer loans | Consumer | Loss    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans   $ 0