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Indebtedness (Narrative) (Details) $ in Millions | 12 Months Ended |  |
--- | --- | --- | ---
Sep. 30, 2018 USD ($) | Mar. 21, 2018 | Mar. 20, 2018
Debt Instrument [Line Items] |  |  |
Current Fiscal Year End Date | --09-30 |  |
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate | 2.25% | 2.00% |
Letters of Credit Maximum Issuance Available | $ 75.0 |  |
Letters of Credit Outstanding, Amount | 31.4 |  |
Debt Instrument, Unused Borrowing Capacity, Amount | 138.2 |  |
Debt Instrument, Periodic Payment, Principal | $ 10.7 |  |
Maximum Leverage Ratio |  | 4.5 | 4.0
Pro Forma Leverage | 4.0 |  |
Term Loan [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Repayments of Debt | $ 260.0 |  |
Maximum [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Basis Spread on Variable Rate | 2.25% |  |
Minimum [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Basis Spread on Variable Rate | 1.25% |  |
London Interbank Offered Rate (LIBOR) [Member] | Minimum [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 0.00% |  |

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