Quarterly report pursuant to Section 13 or 15(d)

Significant Accounting Policies - Concentration Risks (Details)

v3.22.2
Significant Accounting Policies - Concentration Risks (Details) - Revenues - Customer Concentration Risk
3 Months Ended 9 Months Ended
Jun. 30, 2022
Jun. 30, 2021
Jun. 30, 2022
Jun. 30, 2021
Private        
Concentration Risk [Line Items]        
Concentration risk percentage 36.60% 38.50% 38.80% 40.00%
Public        
Concentration Risk [Line Items]        
Concentration risk percentage 63.40% 61.50% 61.20% 60.00%
Alabama Department of Transportation        
Concentration Risk [Line Items]        
Concentration risk percentage 14.40% 10.90% 10.90% 9.30%
North Carolina Department of Transportation        
Concentration Risk [Line Items]        
Concentration risk percentage 13.60% 12.20% 10.30% 8.70%
Florida Department of Transportation        
Concentration Risk [Line Items]        
Concentration risk percentage 9.20% 7.80% 10.40% 8.50%