Quarterly report pursuant to Section 13 or 15(d)

Organization and Summary of Significant Accounting Policies - Organization (Details)

v3.10.0.1
Organization and Summary of Significant Accounting Policies - Organization (Details)
9 Months Ended
Sep. 30, 2018
vessel
segment
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
Number of operating segments | segment 4
Number of harbor tug vessels 10
Number of offshore vessels 2
Number of additional vessels 7