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Income Taxes (Reconciliation of Statutory Taxes to Effective Taxes) (Details) - USD ($) $ in Millions | 12 Months Ended
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Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2016
Income Tax Disclosure [Abstract] |  |  |
Tax at U.S. federal statutory income tax rate of 35% | $ 23.4 | $ 27.5 | $ 24.3
Adjustments to reconcile to income tax expense (benefit): |  |  |
Federal Valuation Allowance | 0.5 | 0.4 | 0.0
State income taxes, net of federal benefit | 4.8 | 2.7 | 3.1
Domestic production activities deduction | (2.4) | (4.5) | (3.0)
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount | (42.5) | (0.4) | 0.4
Federal transition tax | 7.5 | 0.0 | 0.0
Excess tax benefits related to stock compensation | (0.6) | (2.1) | (0.5)
Tax Credits | (1.7) | (1.4) | (2.0)
Other nondeductible expenses | 0.5 | 0.6 | 0.7
Foreign income taxes | 0.0 | 0.3 | 0.2
Nondeductible compensation | 0.2 | 0.5 | 0.4
Other income tax | 0.4 | 0.6 | 0.6
Income tax expense (benefit) | $ (9.9) | $ 24.2 | $ 24.2

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