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Allowance for Losses on Loans - Narrative (Details) - USD ($) | 3 Months Ended |
--- | --- | ---
Dec. 31, 2024 | Dec. 31, 2023 | Sep. 30, 2024
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Provision for credit losses | $ 0 | $ 0 |
Allowance for credit loss, charge-off (recovery) | 231,000 | $ (113,000) |
Gross loans | $ 21,265,023,000 |  | $ 21,120,107,000
Percent past due | 0.30% |  | 0.25%
Financial Asset Originated |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Non-accrual | $ 72,487,000 |  | $ 69,541,000
Non-Performing Loans |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Gross loans | $ 79,113,000 |  | $ 77,418,000
Ratio of non-performing assets to total assets | 0.29% |  | 0.28%
Commercial loans |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Gross loans | $ 12,284,931,000 |  | $ 12,205,420,000
Percent past due | 0.25% |  | 0.16%
Commercial loans | Financial Asset Originated |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Non-accrual | $ 52,956,000 |  | $ 46,299,000
Commercial loans | Commercial & industrial |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Gross loans | $ 2,403,719,000 |  | $ 2,332,732,000
Percent past due | 0.09% |  | 0.09%
Commercial loans | Commercial & industrial | Financial Asset Originated |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Non-accrual | $ 1,963,000 |  | $ 0

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- Definition Amount, excluding accrued interest, of decrease (increase) in allowance for credit loss on financing receivable from writeoff (recovery). Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 13 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-13 + Details
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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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