Income taxes - Summary of Income Tax Contingencies (Details) - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Sep. 30, 2017 |
Sep. 30, 2016 |
Sep. 30, 2015 |
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| Reconciliation of the beginning and ending amount of gross unrecognized tax benefits | |||
| Balance at beginning of year | $ 448 | $ 529 | $ 812 |
| Lapse of statute of limitation | 0 | 0 | (200) |
| Increases for tax positions taken in current year | 185 | 0 | 0 |
| Reductions for tax positions of prior years | 0 | (81) | (83) |
| Balance at end of year | $ 633 | $ 448 | $ 529 |
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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/presentationRef
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- Definition Amount of decrease in unrecognized tax benefits resulting from tax positions taken in prior period tax returns. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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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://www.xbrl.org/2003/role/presentationRef
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- Definition Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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