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Organization and Summary of Significant Accounting Policies - Additional Information (Details) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2019 USD ($) segment vessel ferry tug ship towboat | Dec. 31, 2018 USD ($) segment | Jan. 01, 2018 USD ($)
Significant Accounting Policies [Line Items] |  |  |
Number of operating segments | segment | 3 | 4 |
Number of corporate non-operating segments | segment | 1 | 1 |
Number of harbor tug vessels | 4 |  |
Number of regional class research vessels | 3 |  |
Number of ferries | ferry | 3 |  |
Number of ice-breaker tug vessels | tug | 1 |  |
Number of towing, salvage and rescue vessels | ship | 3 |  |
Number of OSVs | 2 |  |
Number of harbor tug vessels | 6 |  |
Number of towboats | towboat | 2 |  |
Prepaid contract costs | $ | $ 0 | $ 0 |
Accounting Standards Update 2014-09 |  |  |
Significant Accounting Policies [Line Items] |  |  |
Cumulative effect of new accounting principle in period of adoption | $ |  |  | $ 0
Minimum |  |  |
Significant Accounting Policies [Line Items] |  |  |
Property, plant and equipment, useful life | 3 years |  |
Maximum |  |  |
Significant Accounting Policies [Line Items] |  |  |
Property, plant and equipment, useful life | 25 years |  |

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