Revenue recognition - Accounts Receivable Reserves (Details) - Accounts receivable, billed and unbilled - USD ($) $ in Thousands |
12 Months Ended | ||
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Sep. 30, 2020 |
Sep. 30, 2019 |
Sep. 30, 2018 |
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| Changes in the reserves against current billed accounts receivable | |||
| Balance at beginning of year | $ 5,382 | $ 4,285 | $ 6,843 |
| Additions to reserve | 12,976 | 4,018 | 243 |
| Deductions | (12,307) | (2,921) | (2,801) |
| Balance at end of year | $ 6,051 | $ 5,382 | $ 4,285 |
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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. No definition available.
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- Definition Amount of valuation and qualifying accounts and reserves. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Amount of increase in valuation and qualifying accounts and reserves from charge to cost and expense. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Amount of decrease in valuation and qualifying accounts and reserves. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Details
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