Quarterly report pursuant to Section 13 or 15(d)

ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Organization (Details)

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ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Organization (Details)
6 Months Ended 12 Months Ended
Jun. 30, 2019
ferries
ship
vessel
towboat
segment
tug
Dec. 31, 2018
segment
Organization, Consolidation and Presentation of Financial Statements [Abstract]    
Number of operating segments | segment 3 4
Number of corporate non-operating segments | segment 1 1
Number of harbor tug vessels 6  
Number of offshore vessels 3  
Number of ferries | ferries 2  
Number of towboats | towboat 2  
Number of towing, salvage and rescue vessels | ship 3  
Number of OSVs 2  
Number of harbor tug vessels 4  
Number of ice-breaker tug vessels | tug 1