Significant Accounting Policies - Consolidation of Revenues (Detail) - Revenues [Member] - Customer Concentration Risk [Member] |
3 Months Ended | 9 Months Ended | ||
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Jun. 30, 2018 |
Jun. 30, 2017 |
Jun. 30, 2018 |
Jun. 30, 2017 |
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Alabama Department of Transportation [Member] | ||||
Concentration Risk [Line Items] | ||||
Concentration risk percentage | 17.00% | 13.60% | 14.80% | 12.80% |
North Carolina Department of Transportation [Member] | ||||
Concentration Risk [Line Items] | ||||
Concentration risk percentage | 14.80% | 16.60% | 13.50% | 13.20% |
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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. No definition available.
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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://fasb.org/us-gaap/role/ref/legacyRef
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