Earnings per share - Narrative (Details) - shares |
12 Months Ended | ||
|---|---|---|---|
Sep. 30, 2018 |
Sep. 30, 2017 |
Sep. 30, 2016 |
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| Unvested restricted stock units | |||
| Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] | |||
| Awards excluded from the calculation of diluted earnings per share (in shares) | 5,000 | 9,000 | 21,000 |
| X | ||||||||||
- Definition Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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| X | ||||||||||
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available.
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| X | ||||||||||
- Details
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