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Income Taxes (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Sep. 30, 2019 | Sep. 30, 2018 | Sep. 30, 2017
Income Taxes |  |  |  |  |
Federal statutory rate (as a percent) |  |  | 21.00% |  | 35.00%
Blended statutory rate (as a percentage) |  |  |  | 24.50% |
Effective tax rate (as a percent) | (60.90%) | 27.40% |  |  |
Net benefit from Tax Cuts and Jobs Acts of 2017 | $ 41.7 |  |  |  |
Benefit from change in uncertain tax positions in US and Canada | 11.2 |  |  |  |
Benefit from income tax credits and incentives | 8.4 |  |  |  |
Provisional amount related to remeasurement of deferred tax balance | 36.1 |  |  |  |
Provisional amount of tax benefit related to releasing of deferred tax liability | 77.0 |  |  |  |
Provisional amount of income tax expense related to transition tax on foreign subsidiaries | 71.4 |  |  |  |
Decrease in liability for uncertain tax positions | $ (15.0) |  |  |  |
Gross book-tax differences from non-U.S. subsidiaries |  |  |  |  | $ 1,700.0

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