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Segment Information, Geographical Data and Major Customers (Parenthetical) (Detail) - USD ($) |  |  |  |  | 4 Months Ended | 5 Months Ended | 12 Months Ended
--- | --- | --- | --- | --- | --- | --- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Jul. 31, 2017 | Mar. 31, 2017 | Jul. 31, 2017 | Dec. 31, 2017 | Dec. 31, 2018 | Mar. 31, 2017
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
General and administrative expenses |  |  |  |  |  | $ 46,619,000 | $ 110,023,000 |
Construction costs | $ 0 | $ 9,300 |  |  |  |  |  |
Predecessor |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
General and administrative expenses |  |  |  |  | $ 41,832,000 |  |  | $ 145,879,000
Construction costs |  |  | $ 47,500 | $ 52,400 |  |  |  |
Corporate | GulfMark |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Merger and integration costs |  |  |  |  |  |  | $ 13,200,000 |
Corporate | Predecessor | Troms Offshore Supply AS |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
General and administrative expenses |  |  |  |  | $ 6,700,000 |  |  | $ 29,000,000

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