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ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Organization (Details) | 6 Months Ended | 12 Months Ended
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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 |

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- Definition Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues. + References No definition available. + Details
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