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Borrowing Arrangements (Narrative) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2019
Debt Instrument [Line Items] |  |  |
Outstanding Letter Of Credit Accrued Fees And Expenses | $ 1.3 |  |
Outstanding Letter Of Credit Accrued Fees And Expenses | 1.3 |  |
Long-Term Debt, Maturity, Year One | 1.0 |  |
Long-Term Debt, Maturity, Year Two | 0.7 |  |
Long-Term Debt, Maturity, Year Three | 0.3 |  |
Long-Term Debt, Maturity, Year Four | 0.1 |  |
Long-Term Debt, Maturity, Year Five | $ 0.1 |  |
Line of Credit Facility, Expiration Date | Jul. 29, 2025 |  |
Outstanding Letter of Credit | $ 15.0 |  |
Gain (Loss) on Extinguishment of Debt | (16.7) | $ 0.0 | $ 0.0
Payment for Debt Extinguishment or Debt Prepayment Cost | 12.4 |  |
Write off of Deferred Debt Issuance Cost | 4.3 |  |
4.0% Senior Notes |  |  |
Debt Instrument [Line Items] |  |  |
Payments of Debt Issuance Costs | 5.5 |  |
Financial Liabilities Fair Value Disclosure | 467.3 |  |
Payments of Debt Issuance Costs | 5.5 |  |
Financial Liabilities Fair Value Disclosure | 467.3 |  |
Revolving Credit Facility [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Line of Credit Facility, Maximum Borrowing Capacity |  | 175.0 |
Potential Increase In The Size Of Credit Facility | $ 150.0 |  |
Line of Credit Facility, Interest Rate at Period End | 200.00% |  |
Maximum excess availability level at which financial maintenance covenants would apply | $ 17.5 |  |
Maximum excess availability level at which financial maintenance covenants would apply, as a percentage of aggregate commitments | 10.00% |  |
Line of Credit Facility, Remaining Borrowing Capacity | $ 158.7 |  |
Line of Credit Facility, Remaining Borrowing Capacity | 158.7 |  |
Potential Increase In The Size Of Credit Facility | $ 150.0 |  |
Line of Credit Facility, Maximum Borrowing Capacity |  | $ 175.0 |
Line of Credit Facility, Interest Rate at Period End | 200.00% |  |
Maximum excess availability level at which financial maintenance covenants would apply | $ 17.5 |  |
Maximum excess availability level at which financial maintenance covenants would apply, as a percentage of aggregate commitments | 10.00% |  |
Bonds [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Interest Rate, Effective Percentage | 4.00% | 5.50% |
Debt Instrument, Interest Rate, Effective Percentage | 4.00% | 5.50% |
Swing Line Loans [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Line of Credit Facility, Maximum Borrowing Capacity | $ 25.0 |  |
Line of Credit Facility, Maximum Borrowing Capacity | 25.0 |  |
Letter Of Credit [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Line of Credit Facility, Maximum Borrowing Capacity | 60.0 |  |
Line of Credit Facility, Maximum Borrowing Capacity | $ 60.0 |  |
London Interbank Offered Rate (LIBOR) [Member] | Minimum [Member] | Revolving Credit Facility [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Basis Spread on Variable Rate | 200.00% |  |
Debt Instrument, Basis Spread on Variable Rate | 200.00% |  |
London Interbank Offered Rate (LIBOR) [Member] | Maximum [Member] | Revolving Credit Facility [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Basis Spread on Variable Rate | 225.00% |  |
Debt Instrument, Basis Spread on Variable Rate | 225.00% |  |
Base Rate [Member] | Minimum [Member] | Revolving Credit Facility [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Basis Spread on Variable Rate | 100.00% |  |
Debt Instrument, Basis Spread on Variable Rate | 100.00% |  |
Base Rate [Member] | Maximum [Member] | Revolving Credit Facility [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Basis Spread on Variable Rate | 125.00% |  |
Debt Instrument, Basis Spread on Variable Rate | 125.00% |  |

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