Schedule of Segment Reporting Information, Revenue by Vessel Class (Detail) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 162,430	$ 298,313
Americas Fleet Deepwater vessels
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 40,387	$ 80,152
Percentage of revenue	25.00%	27.00%
Americas Fleet Towing-Supply/supply
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 16,879	$ 29,515
Percentage of revenue	10.00%	10.00%
Americas Fleet Other
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 3,342	$ 4,505
Percentage of revenue	2.00%	1.00%
Americas Fleet
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 60,608	$ 114,172
Percentage of revenue	37.00%	38.00%
Asia and Pacific Fleet Deepwater vessels
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 2,590	$ 19,833
Percentage of revenue	2.00%	7.00%
Asia/Pacific Fleet Towing-Supply/supply
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 5,331	$ 8,104
Percentage of revenue	3.00%	2.00%
Asia/Pacific Fleet
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 7,921	$ 27,937
Percentage of revenue	5.00%	9.00%
Middle East Fleet Deepwater vessels
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 6,038	$ 6,691
Percentage of revenue	4.00%	2.00%
Middle East Fleet Towing-Supply/supply
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 18,164	$ 25,562
Percentage of revenue	11.00%	9.00%
Middle East fleet
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 24,202	$ 32,253
Percentage of revenue	15.00%	11.00%
Africa/Europe Fleet Deepwater vessels
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 33,289	$ 67,661
Percentage of revenue	20.00%	23.00%
Africa/Europe Fleet Towing-Supply/supply
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 27,917	$ 41,825
Percentage of revenue	18.00%	14.00%
Africa And Europe Fleet Other
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 8,493	$ 14,465
Percentage of revenue	5.00%	5.00%
Africa/Europe Fleet
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 69,699	$ 123,951
Percentage of revenue	43.00%	42.00%
Worldwide Fleet Deepwater vessels
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 82,304	$ 174,337
Percentage of revenue	51.00%	59.00%
Worldwide Fleet Towing-Supply/supply
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 68,291	$ 105,006
Percentage of revenue	42.00%	35.00%
Worldwide Fleet Other
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 11,835	$ 18,970
Percentage of revenue	7.00%	6.00%
Worldwide Fleet
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 162,430	$ 298,313
Percentage of revenue	100.00%	100.00%