| Leases - Narrative (Details) $ in Millions | 9 Months Ended | 
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| Jun. 30, 2020  USD ($) | |
| Leases [Abstract] | |
| Weighted average incremental borrowing rate | 3.80% | 
| Weighted average remaining lease term | 2 years 10 months 24 days | 
| Operating lease payments | $ 83.7 | 
| Operating lease liabilities arising from new or remeasured right-of-use assets | $ 39.9 | 
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- References No definition available. 
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- Definition Amount of cash outflow from operating lease, excluding payments to bring another asset to condition and location necessary for its intended use. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Definition Weighted average discount rate for operating lease calculated at point in time. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Definition Weighted average remaining lease term for operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Reference 1: http://www.xbrl.org/2003/role/exampleRef 
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- Definition Amount of increase in right-of-use asset obtained in exchange for operating lease liability. Reference 1: http://www.xbrl.org/2003/role/exampleRef 
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