Quarterly report pursuant to Section 13 or 15(d)

Related Parties - Additional Information (Detail)

v3.8.0.1
Related Parties - Additional Information (Detail) - USD ($)
3 Months Ended 6 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Mar. 31, 2018
Mar. 31, 2017
Dec. 31, 2017
Sep. 30, 2017
Related Party Transaction [Line Items]            
Cost of revenues $ 105,150,000 $ 96,005,000 $ 232,773,000 $ 199,396,000    
Accounts payable 37,324,000   37,324,000     $ 52,402,000
Related Parties [Member]            
Related Party Transaction [Line Items]            
Note receivable as consideration for sale of the wholly-owned subsidiary         $ 1,000,000  
Related Parties [Member] | Construction Services One [Member]            
Related Party Transaction [Line Items]            
Revenue 300,000 700,000 1,500,000 1,800,000    
Contract receivable 4,600,000   4,600,000     5,300,000
Related Parties [Member] | Construction Services Two [Member]            
Related Party Transaction [Line Items]            
Revenue 100,000 0 200,000 0    
Contract receivable 600,000   600,000     1,000,000
Austin Trucking [Member]            
Related Party Transaction [Line Items]            
Cost of revenues 1,400,000 1,500,000 4,300,000 4,400,000    
Accounts payable 500,000   500,000     $ 1,000,000
SunTx [Member] | Management Service Agreement [Member]            
Related Party Transaction [Line Items]            
Related party expense 250,000          
Payment to related party 300,000 $ 400,000 700,000 $ 700,000    
SunTx [Member] | Management Service Agreement [Member] | Other Noncurrent Assets [Member]            
Related Party Transaction [Line Items]            
Related party expense 100,000          
Accounts Payable [Member] | Related Parties [Member]            
Related Party Transaction [Line Items]            
Note receivable as consideration for sale of the wholly-owned subsidiary $ 900,000   $ 900,000