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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

X

- Definition

Costs incurred to effect a business combination which have been expensed during the period. Such costs could include business integration costs, systems integration and conversion costs, and severance and other employee-related costs.

+ References

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- Definition

The aggregate costs related to goods produced and sold and services rendered by an entity during the reporting period. This excludes costs incurred during the reporting period related to financial services rendered and other revenue generating activities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.2(a),(d))
-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227

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- Definition

The aggregate total of expenses of managing and administering the affairs of an entity, including affiliates of the reporting entity, which are not directly or indirectly associated with the manufacture, sale or creation of a product or product line.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
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-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227

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