v3.26.1
Allowance for Losses on Loans - Schedule of Loans Based on Credit Quality Indicators (Details) - USD ($)
$ in Thousands
9 Months Ended 12 Months Ended
Jun. 30, 2026
Sep. 30, 2025
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans $ 20,232,707 $ 20,288,338
Pass    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans $ 19,018,709 $ 19,406,000
Pass | Accounts Receivable | Credit Concentration Risk    
Financing Receivable, Credit Quality Indicator [Line Items]    
Total grade as a % of total loans at amortized cost 94.00% 95.70%
Watch    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans $ 227,903  
Watch | Accounts Receivable | Credit Concentration Risk    
Financing Receivable, Credit Quality Indicator [Line Items]    
Total grade as a % of total loans at amortized cost 1.10%  
Special Mention    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans $ 466,648 $ 247,830
Special Mention | Accounts Receivable | Credit Concentration Risk    
Financing Receivable, Credit Quality Indicator [Line Items]    
Total grade as a % of total loans at amortized cost 2.30% 1.20%
Substandard    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans $ 464,136 $ 629,353
Substandard | Accounts Receivable | Credit Concentration Risk    
Financing Receivable, Credit Quality Indicator [Line Items]    
Total grade as a % of total loans at amortized cost 2.30% 3.10%
Doubtful    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans $ 55,311 $ 5,131
Doubtful | Accounts Receivable | Credit Concentration Risk    
Financing Receivable, Credit Quality Indicator [Line Items]    
Total grade as a % of total loans at amortized cost 0.30% 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 at amortized cost   0.00%
Commercial loans    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans $ 12,574,277 $ 11,851,657
Commercial loans | Pass    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 11,384,744 10,994,504
Commercial loans | Watch    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 227,903  
Commercial loans | Special Mention    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 466,648 247,830
Commercial loans | Substandard    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 439,671 604,168
Commercial loans | Doubtful    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 55,311 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 4,645,902 4,631,321
Commercial loans | Multi-family | Pass    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 4,208,611 4,337,347
Commercial loans | Multi-family | Watch    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 73,911  
Commercial loans | Multi-family | Special Mention    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 205,789 136,817
Commercial loans | Multi-family | Substandard    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 155,259 154,807
Commercial loans | Multi-family | Doubtful    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 2,332 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 3,626,043 3,588,950
Commercial loans | Commercial real estate | Pass    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 3,409,300 3,339,062
Commercial loans | Commercial real estate | Watch    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 74,766  
Commercial loans | Commercial real estate | Special Mention    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 25,724 61,580
Commercial loans | Commercial real estate | Substandard    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 116,253 185,527
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 3,101,192 2,386,363
Commercial loans | Commercial & industrial | Pass    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 2,713,652 2,086,750
Commercial loans | Commercial & industrial | Watch    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 77,533  
Commercial loans | Commercial & industrial | Special Mention    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 94,991 44,998
Commercial loans | Commercial & industrial | Substandard    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 162,037 254,591
Commercial loans | Commercial & industrial | Doubtful    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 52,979 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 1,015,908 1,105,101
Commercial loans | Construction | Pass    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 878,352 1,091,682
Commercial loans | Construction | Watch    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 994  
Commercial loans | Construction | Special Mention    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 136,562 4,435
Commercial loans | Construction | Substandard    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 0 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 185,232 139,922
Commercial loans | Land - acquisition & development | Pass    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 174,829 139,663
Commercial loans | Land - acquisition & development | Watch    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 699  
Commercial loans | Land - acquisition & development | Special Mention    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 3,582 0
Commercial loans | Land - acquisition & development | Substandard    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 6,122 259
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 7,658,430 8,436,681
Consumer loans | Pass    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 7,633,965 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 24,465 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 16,417 78,243
Consumer loans | Construction | Pass    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 15,525 77,483
Consumer loans | Construction | Watch    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 0  
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 892 760
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 7,268,163 7,936,931
Consumer loans | Single-family residential | Pass    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 7,245,719 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 22,444 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 71,982 88,696
Consumer loans | Land - consumer lot loans | Pass    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 71,743 88,613
Consumer loans | Land - consumer lot loans | Watch    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 0  
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 239 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 247,584 271,286
Consumer loans | HELOC | Pass    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 246,956 270,874
Consumer loans | HELOC | Watch    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 0  
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 628 412
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 54,284 61,525
Consumer loans | Consumer | Pass    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 54,022 61,406
Consumer loans | Consumer | Watch    
Financing Receivable, Credit Quality Indicator [Line Items]    
Gross loans 0  
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 262 119
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