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Income Taxes (Narrative) (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Dec. 31, 2018 | Mar. 31, 2018 | Dec. 31, 2017 | Sep. 30, 2017 | Sep. 30, 2018
Income Tax Disclosure [Abstract] |  |  |  |  |
Unrecognized Tax Benefits | $ 3.4 |  |  |  | $ 3.3
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent | 21.00% |  | 24.50% | 35.00% |
Weighted Average Deferred Income Tax Provision Rate |  |  | 25.00% | 39.00% |
Transition Tax Expense | $ 6.9 | $ 7.5 |  |  |
Transition Tax True-up | $ 0.6 |  |  |  |

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