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Accounts Receivable - Additional Information (Detail) - USD ($)
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Dec. 31, 2016
Receivables [Abstract]          
Amount billed but not received under retainage provisions in contracts $ 2,600,000   $ 2,600,000   $ 3,200,000
Retainage receivables on contracts period     1 year    
Provision for doubtful accounts $ 1,200,000 $ 30,000 $ 2,184,000 $ 324,000