Accounts receivable reserves - Schedule of Accounts Receivable Reserve (Details) - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Sep. 30, 2018 |
Sep. 30, 2017 |
Sep. 30, 2016 |
|
| Changes in the reserves against current billed accounts receivable | |||
| Contractual retainage provisions | $ 13,400 | $ 10,300 | |
| Accounts receivable, billed and unbilled | |||
| Changes in the reserves against current billed accounts receivable | |||
| Balance at beginning of year | 6,843 | 4,226 | $ 3,385 |
| Additions to reserve | 243 | 5,106 | 2,335 |
| Deductions | (2,801) | (2,489) | (1,494) |
| Balance at end of year | $ 4,285 | $ 6,843 | $ 4,226 |
| X | ||||||||||
- Definition Amount billed to customers under long-term contracts or programs that have been withheld because of retainage provisions in a contract. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
|
| X | ||||||||||
- 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.
|
| X | ||||||||||
- Definition Amount of valuation and qualifying accounts and reserves. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|
| X | ||||||||||
- 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
|
| X | ||||||||||
- Definition Amount of decrease in valuation and qualifying accounts and reserves. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|
| X | ||||||||||
- Details
|