Quarterly report pursuant to Section 13 or 15(d)

REVENUE, CONTRACT ASSETS AND LIABILITIES AND OTHER CONTRACT MATTERS - Narrative (Details)

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REVENUE, CONTRACT ASSETS AND LIABILITIES AND OTHER CONTRACT MATTERS - Narrative (Details)
$ in Thousands
3 Months Ended
Mar. 31, 2019
USD ($)
vessel
Mar. 31, 2018
USD ($)
Dec. 31, 2018
USD ($)
Long-term Contracts or Programs Disclosure [Line Items]      
Bad debt expense $ 53 $ 8  
Allowance for bad debt $ 400   $ 400
Number of harbor tug vessels | vessel 8    
Shipyard      
Long-term Contracts or Programs Disclosure [Line Items]      
Reduction to estimated contract price $ 1,300