Income taxes - Summary of Income Tax Contingencies (Details) - USD ($) $ in Thousands |
12 Months Ended | ||
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Sep. 30, 2019 |
Sep. 30, 2018 |
Sep. 30, 2017 |
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| Reconciliation of the beginning and ending amount of gross unrecognized tax benefits | |||
| Balance at beginning of year | $ 721 | $ 633 | $ 448 |
| Increases for tax positions taken in current year | 2,280 | 88 | 185 |
| Balance at end of year | $ 3,001 | $ 721 | $ 633 |
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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 unrecognized tax benefits. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Amount of increase (decrease) in unrecognized tax benefits attributable to uncertain tax positions taken in tax returns. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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