Significant Accounting Policies - Concentration of Risks (Details) - Revenues - Customer Concentration Risk |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2025 |
Jun. 30, 2024 |
Jun. 30, 2025 |
Jun. 30, 2024 |
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| Private | ||||
| Concentration Risk [Line Items] | ||||
| Concentration risk percentage | 35.10% | 35.60% | 39.00% | 39.20% |
| Public | ||||
| Concentration Risk [Line Items] | ||||
| Concentration risk percentage | 64.90% | 64.40% | 61.00% | 60.80% |
| North Carolina Department of Transportation | ||||
| Concentration Risk [Line Items] | ||||
| Concentration risk percentage | 12.50% | 10.30% | ||
| Florida Department of Transportation | ||||
| Concentration Risk [Line Items] | ||||
| Concentration risk percentage | 13.40% | 13.90% | ||
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- 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. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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