XML 51 R39.htm IDEA: XBRL DOCUMENT v3.8.0.1
Accounts Receivable - Additional Information (Detail) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Dec. 31, 2017
Receivables [Abstract]      
Amount billed but not received under retainage provisions in contracts $ 2,700   $ 2,500
Retainage receivables on contracts period 1 year    
Bad debt expense $ 146 $ 217