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v3.19.3.a.u2

Nature of Operations and Summary of Significant Accounting Policies - Additional Information (Detail) $ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2019 USD ($) Vessel | Dec. 31, 2018 Vessel | Jan. 01, 2019 USD ($)
Property, Plant and Equipment [Line Items] |  |  |
Extended useful life, months | 30 months |  |
Inspection interval | The majority of our vessels require certification inspections twice in every five year period |  |
Number of Offshore Supply Vessels | 217 | 257 |
Number of Vessels Disposed | 40 |  |
Number Of Assets Held For Sale | 46 |  |
Number of Vessel Sold | 40 |  |
Right of use assets | $ | $ 4,338 |  |
Lease liabilities | $ | $ 4,775 |  |
Accounting Standards Update 2016-02 |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Right of use assets | $ |  |  | $ 5,000
Lease liabilities | $ |  |  | $ 5,400
Marine Equipment |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Percentage of salvage values | 7.50% |  |
Remaining Number Of Vessels |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Remaining Number Of Vessels | 171 |  |
Actively Employed Vessels |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Remaining Number Of Vessels | 152 |  |
Stacked Vessels |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Number Of Assets Held For Sale | 46 |  |
Remaining Number Of Vessels | 19 |  |
Minimum | Marine Equipment | From Date of Construction |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Estimated useful lives, years | 10 years |  |
Minimum | Other Property Plant and Equipment |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Estimated useful lives, years | 3 years |  |
Maximum |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Highly liquid investments, maturities | 3 months |  |
Maximum | Marine Equipment | From Date of Construction |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Estimated useful lives, years | 20 years |  |
Maximum | Other Property Plant and Equipment |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Estimated useful lives, years | 10 years |  |

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