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Nature of Operations and Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2018 | Mar. 31, 2017 | Jan. 01, 2019
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 |  |
Subsequent Event | Accounting Standards Update 2016-06 |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Lease assets |  |  | $ 4.5
Lease liabilities |  |  | $ 6.0
Marine Equipment |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Percentage of salvage values | 7.50% |  |
Stacked Vessels |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Property plant and equipment average age | 9 years 9 months 18 days | 11 years |
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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