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Receivables from customers, net and notes receivable, net - Allowance for Bad Debts Rollforward (Details) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Sep. 30, 2019 | Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2016
Receivables from customers and notes receivable, net [Abstract] |  |  |  |
SEC Schedule, 12-09, Valuation Allowances and Reserves, Amount | $ 48.6 | $ 58.2 | $ 54.6 | $ 9.7
Allowance for Doubtful Accounts Receivable [Roll Forward] |  |  |  |
Provision for bad debts | (9.8) | 3.9 | 51.0 |
Allowance for Doubtful Accounts Receivable, Charge-offs | 1.3 | 0.3 | 6.1 |
Allowance for Doubtful Accounts Receivable, Recoveries | 0.4 | 0.1 |  |
SEC Schedule, 12-09, Valuation Allowances and Reserves, Increase (Decrease) Adjustment | $ 1.5 | $ 0.0 | $ 0.0 |

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- Definition Receivables from customers and notes receivable, net [Abstract] + References No definition available. + Details
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- Definition Amount of recoveries of receivables doubtful of collection that were previously charged off. + References No definition available. + Details
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- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
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- Definition Amount of increase (decrease) in valuation and qualifying accounts and reserves from adjustment. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 4 -Subparagraph (SX 210.12-09) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690 + Details
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- Definition Amount of valuation and qualifying accounts and reserves. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 4 -Subparagraph (SX 210.12-09) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690 + Details
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- Definition Amount of increase in valuation and qualifying accounts and reserves from charge to cost and expense. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 4 -Subparagraph (SX 210.12-09) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690 + Details
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- Definition Amount of decrease in valuation and qualifying accounts and reserves. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 4 -Subparagraph (SX 210.12-09) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690 + Details
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