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Retirement and Postretirement Employee Benefit Plans - Narrative (Details) $ in Thousands |  | 12 Months Ended
--- | --- | ---
Jan. 01, 2026 | Sep. 30, 2025 USD ($) plan shares | Sep. 30, 2024 USD ($) shares | Sep. 30, 2023 USD ($)
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Recovery period |  | 15 years |  |
Supplemental Executive Benefit Plan |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Number of nonqualified supplemental plans offered | plan |  | 3 |  |
Retirement Savings Plan |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
New employee contribution percentage |  | 5.00% |  |
Years of service |  | 1 year |  |
Maximum of eligible compensation |  | 65.00% |  |
Employer matching, percent of employee salary |  | 5.00% |  |
Automatic increase feature |  | 1.00% |  |
Deferral rate |  | 10.00% |  |
Percent of employee contribution |  | 100.00% |  |
Fixed annual contribution percent |  | 4.00% |  |
Contribution plan cost |  | $ 34,300 | $ 26,800 | $ 23,900
Percent of common stock outstanding |  | 1.10% | 1.20% |
Retirement Savings Plan | Forecast |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Employer matching, percent of employee salary | 6.00% |  |  |
Employee Pension Plan |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Vesting period |  | 3 years |  |
Employer contributions |  | $ 0 | $ 5,000 |
Accounts receivable |  | $ 5,100 | $ 700 |
Employee Pension Plan | Minimum |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Medium-term horizon |  | 3 years |  |
Employee Pension Plan | Maximum |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Medium-term horizon |  | 5 years |  |
Employee Pension Plan | Company stock |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Shares held by plan (in shares) | shares |  | 506,700 | 716,700 |
Percent of plan assets |  | 14.00% | 16.70% |
Dividend income |  | $ 1,900 | $ 2,300 |
Employee Pension Plan | Retirement Savings Plan |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Employer matching, percent of employee salary |  | 10.00% |  |
Supplemental Executive Retirement Plans |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Employer contributions |  | $ 0 | 0 |
Settlement charge |  | 0 | (1,529) | (1,030)
Lump sum settlement |  | 0 | 0 |
Assets held-in-trust |  | $ 30,100 | 31,100 |
Supplemental Executive Retirement Plans | Supplemental Executive Benefit Plan |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Percent of covered compensation |  | 75.00% |  |
Supplemental Executive Retirement Plans | 1998 Supplemental Executive Retirement Plan, Defined Benefit |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Percent of covered compensation |  | 60.00% |  |
Supplemental Executive Retirement Plans | 2009 Supplemental Executive Retirement Plan, Defined Benefit |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Vesting period |  | 3 years |  |
Contribution percent |  | 10.00% |  |
Contribution percent for members |  | 25.00% |  |
Attainment age |  | 55 years |  |
Supplemental Executive Retirement Plans | Executive Officer |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Settlement charge |  |  | (1,500) | (1,000)
Lump sum settlement |  |  | 9,600 | $ 5,600
Postretirement Plan |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Employer contributions |  | $ 0 | $ 0 |
Postretirement Plan | Minimum |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Expected contribution amount |  | 13,000 |  |
Postretirement Plan | Maximum |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Expected contribution amount |  | $ 18,000 |  |
Postretirement Plan | Diversified investment funds |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Percent of plan assets |  | 98.60% | 97.80% |
Maximum investment percent |  | 75.00% |  |

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- Definition Remaining recovery period of regulatory assets for which no return on investment during recovery period is provided, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 980 -SubTopic 340 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147478742/980-340-50-1 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 55 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147478098/980-340-55-2 + Details
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