Segment Information, Geographical Data and Major Customers (Detail) - USD ($)		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information [Line Items]
Total revenues		$ 122,149,000	$ 91,493,000
Operating profit (loss)	[1]	4,310,000	(1,143,000)
Corporate expenses	[1],[2]	(15,200,000)	(6,784,000)
Gain on asset dispositions, net		1,270,000	1,919,000
Asset impairments		0	(6,186,000)	[3]
Operating loss		(9,620,000)	(12,194,000)
Depreciation and amortization		22,932,000	12,017,000
Additions to properties and equipment		3,116,000	1,677,000
All Other Segments
Segment Reporting Information [Line Items]
Operating profit (loss)	[1]	1,704,000	1,506,000
Depreciation and amortization		5,000	5,000
Operating Segments | Americas
Segment Reporting Information [Line Items]
Operating profit (loss)	[1]	(1,030,000)	4,911,000
Depreciation and amortization		6,261,000	3,313,000
Additions to properties and equipment		398,000	1,037,000
Operating Segments | Middle East/Asia Pacific
Segment Reporting Information [Line Items]
Operating profit (loss)	[1]	(1,162,000)	(2,253,000)
Depreciation and amortization		4,450,000	2,769,000
Additions to properties and equipment		1,459,000	423,000
Operating Segments | Europe/Mediterranean Sea
Segment Reporting Information [Line Items]
Operating profit (loss)	[1]	(3,317,000)	(3,554,000)
Depreciation and amortization		7,446,000	1,804,000
Additions to properties and equipment		121,000
Operating Segments | West Africa Segment
Segment Reporting Information [Line Items]
Operating profit (loss)	[1]	8,115,000	(1,753,000)
Depreciation and amortization		4,444,000	4,026,000
Additions to properties and equipment		243,000	1,000
Corporate
Segment Reporting Information [Line Items]
Depreciation and amortization		326,000	100,000
Additions to properties and equipment		895,000	216,000
Service | Operating Segments | Americas
Segment Reporting Information [Line Items]
Total revenues		35,279,000	26,081,000
Service | Operating Segments | Middle East/Asia Pacific
Segment Reporting Information [Line Items]
Total revenues		20,456,000	18,388,000
Service | Operating Segments | Europe/Mediterranean Sea
Segment Reporting Information [Line Items]
Total revenues		28,558,000	9,623,000
Service | Operating Segments | West Africa Segment
Segment Reporting Information [Line Items]
Total revenues		35,369,000	33,402,000
Other Operating Revenues
Segment Reporting Information [Line Items]
Total revenues		$ 2,487,000	$ 3,999,000

[1] Prior to January 1, 2019, we allocated the costs of certain marine operations related to general and administrative functions, such as marine management, engineering, supply chain management, risk management, fleet human resources and health and safety to the segment general and administrative expenses. Beginning on January 1, 2019 our management elected to modify that process in order to better analyze costs and better align the policies of the two combined companies such that all costs related to those previously allocated functions will remain as corporate general and administrative expenses. This change is reflected in the table above for the three month period ended March 31, 2019.

[2] Included in corporate expenses for the three months ended March 31, 2019 were $3.7 million of merger and integration costs related to the business combination with GulfMark.

[3] Refer to Note (14) for additional information regarding asset impairment charges.