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Capitalization (Narrative) (Details) $ in Millions |  | 3 Months Ended | 6 Months Ended |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | ---
Feb. 28, 2022 USD ($) bank | Mar. 31, 2024 USD ($) shares | Mar. 31, 2024 USD ($) shares | Feb. 26, 2027 USD ($) | Apr. 10, 2024 USD ($) | Mar. 08, 2024 USD ($) | Feb. 14, 2024 USD ($) lender | Sep. 30, 2023 USD ($)
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Stock repurchase program, authorized amount |  |  |  |  |  | $ 200.0 |  |
Current Portion of Long-Term Debt |  | $ 0.0 | $ 0.0 |  |  |  |  | $ 0.0
Stock and Benefit Plans |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Share Repurchases (in shares) | shares |  |  | 77,426 |  |  |  |  |
Share Repurchase Plan |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Share Repurchases (in shares) | shares |  | 96,133 |  |  |  |  |  |
Share Repurchases |  | $ 5.0 |  |  |  |  |  |
364-Day Credit Agreement |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Term | 364 days |  |  |  |  |  |  |
Term Loan Agreement |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Maximum borrowing capacity |  |  |  |  |  |  | $ 300.0 |
Number of lenders | lender |  |  |  |  |  |  | 6 |
Term Loan Agreement | Subsequent Event |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Long-term debt, face amount |  |  |  |  | $ 300.0 |  |  |
Credit Agreement |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Number of banks In syndicate | bank | 12 |  |  |  |  |  |  |
Maximum borrowing capacity | $ 1,000.0 |  |  |  |  |  |  |
Credit Agreement | Forecast |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Maximum borrowing capacity |  |  |  | $ 940.0 |  |  |  |
Restricted Stock Units |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Common stock issued (in shares) | shares |  |  | 112,632 |  |  |  |  |
Performance Shares |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Common stock issued (in shares) | shares |  |  | 251,255 |  |  |  |  |
Board Of Directors |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Common stock issued (in shares) | shares |  |  | 18,432 |  |  |  |  |
Officer DCP Plan |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Common stock issued (in shares) | shares |  |  | 3,559 |  |  |  |  |

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