Share-Based Compensation - Schedule of stock-based compensation costs (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Mar. 31, 2020 |
Mar. 31, 2019 |
Mar. 31, 2020 |
Mar. 31, 2019 |
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| Compensation Related Costs [Abstract] | ||||
| Share-based compensation costs | $ 3.4 | $ 3.9 | $ 5.7 | $ 5.8 |
| Less impact of income tax benefit | 0.8 | 0.9 | 1.3 | 1.3 |
| Share-based compensation costs, net of tax | $ 2.6 | $ 3.0 | $ 4.4 | $ 4.5 |
| X | ||||||||||
- Definition Amount of expense for award under share-based payment arrangement. Excludes amount capitalized. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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| X | ||||||||||
- Definition Amount, after tax, of expense for award under share-based payment arrangement. No definition available.
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| X | ||||||||||
- References No definition available.
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| X | ||||||||||
- Definition Amount of tax benefit for recognition of expense of award under share-based payment arrangement. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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