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Allowance for Losses on Loans - Credit Risk Profile Based on Payment Activity (Details) - USD ($) $ in Thousands | Dec. 31, 2024 | Sep. 30, 2024
--- | --- | ---
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | $ 21,265,023 | $ 21,120,107
Commercial loans |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | 12,284,931 | 12,205,420
Commercial loans | Multi-family |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | 4,740,797 | 4,556,200
Commercial loans | Commercial real estate |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | 3,610,758 | 3,732,155
Commercial loans | Commercial & industrial |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | 2,403,719 | 2,332,732
Commercial loans | Construction |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | 1,383,048 | 1,424,016
Commercial loans | Land - acquisition & development |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | 146,609 | 160,317
Consumer loans |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | 8,980,092 | 8,914,687
Consumer loans | Construction |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | 155,714 | 182,415
Consumer loans | Single-family residential |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | 8,362,881 | 8,280,300
Consumer loans | Land - consumer lot loans |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | 106,489 | 108,060
Consumer loans | HELOC |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | 279,039 | 269,857
Consumer loans | Consumer |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | 75,969 | 74,055
Performing Loans |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | $ 21,192,536 | $ 21,050,566
% of Total Loans | 99.70% | 99.70%
Performing Loans | Commercial loans |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | $ 12,231,975 | $ 12,159,121
% of Total Loans | 99.60% | 99.60%
Performing Loans | Commercial loans | Multi-family |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | $ 4,716,720 | $ 4,537,457
% of Total Loans | 99.50% | 99.60%
Performing Loans | Commercial loans | Commercial real estate |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | $ 3,584,466 | $ 3,705,793
% of Total Loans | 99.30% | 99.30%
Performing Loans | Commercial loans | Commercial & industrial |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | $ 2,401,756 | $ 2,332,732
% of Total Loans | 99.90% | 100.00%
Performing Loans | Commercial loans | Construction |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | $ 1,382,424 | $ 1,422,896
% of Total Loans | 100.00% | 99.90%
Performing Loans | Commercial loans | Land - acquisition & development |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | $ 146,609 | $ 160,243
% of Total Loans | 100.00% | 100.00%
Performing Loans | Consumer loans |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | $ 8,960,561 | $ 8,891,445
% of Total Loans | 99.80% | 99.70%
Performing Loans | Consumer loans | Construction |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | $ 154,866 | $ 181,567
% of Total Loans | 99.50% | 99.50%
Performing Loans | Consumer loans | Single-family residential |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | $ 8,345,441 | $ 8,258,812
% of Total Loans | 99.80% | 99.70%
Performing Loans | Consumer loans | Land - consumer lot loans |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | $ 106,481 | $ 108,060
% of Total Loans | 100.00% | 100.00%
Performing Loans | Consumer loans | HELOC |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | $ 278,253 | $ 269,261
% of Total Loans | 99.70% | 99.80%
Performing Loans | Consumer loans | Consumer |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | $ 75,520 | $ 73,745
% of Total Loans | 99.40% | 99.60%
Non-Performing Loans |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | $ 72,487 | $ 69,541
% of Total Loans | 0.30% | 0.30%
Non-Performing Loans | Commercial loans |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | $ 52,956 | $ 46,299
% of Total Loans | 0.40% | 0.40%
Non-Performing Loans | Commercial loans | Multi-family |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | $ 24,077 | $ 18,743
% of Total Loans | 0.50% | 0.40%
Non-Performing Loans | Commercial loans | Commercial real estate |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | $ 26,292 | $ 26,362
% of Total Loans | 0.70% | 0.70%
Non-Performing Loans | Commercial loans | Commercial & industrial |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | $ 1,963 | $ 0
% of Total Loans | 0.10% | 0.00%
Non-Performing Loans | Commercial loans | Construction |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | $ 624 | $ 1,120
% of Total Loans | 0.00% | 0.10%
Non-Performing Loans | Commercial loans | Land - acquisition & development |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | $ 0 | $ 74
% of Total Loans | 0.00% | 0.00%
Non-Performing Loans | Consumer loans |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | $ 19,531 | $ 23,242
% of Total Loans | 0.20% | 0.30%
Non-Performing Loans | Consumer loans | Construction |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | $ 848 | $ 848
% of Total Loans | 0.50% | 0.50%
Non-Performing Loans | Consumer loans | Single-family residential |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | $ 17,440 | $ 21,488
% of Total Loans | 0.20% | 0.30%
Non-Performing Loans | Consumer loans | Land - consumer lot loans |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | $ 8 | $ 0
% of Total Loans | 0.00% | 0.00%
Non-Performing Loans | Consumer loans | HELOC |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | $ 786 | $ 596
% of Total Loans | 0.30% | 0.20%
Non-Performing Loans | Consumer loans | Consumer |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |
Amount | $ 449 | $ 310
% of Total Loans | 0.60% | 0.40%

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- Definition Amortized cost excluding accrued interest, before allowance for credit loss, of financing receivable. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479344/326-20-45-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3B -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-3B Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-5 + Details
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