Schedule of Segment Reporting Information, Revenue by Vessel Class (Detail) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 112,257	$ 162,430
Americas Fleet Deepwater vessels
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 17,313	$ 40,387
Percentage of revenue	15.00%	25.00%
Americas Fleet Towing-Supply/supply
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 11,274	$ 16,879
Percentage of revenue	10.00%	10.00%
Americas Fleet Other
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 3,300	$ 3,342
Percentage of revenue	3.00%	2.00%
Americas Fleet
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 31,887	$ 60,608
Percentage of revenue	28.00%	37.00%
Asia and Pacific Fleet Deepwater vessels
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 1,154	$ 2,590
Percentage of revenue	1.00%	2.00%
Asia/Pacific Fleet Towing-Supply/supply
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 3,473	$ 5,331
Percentage of revenue	3.00%	3.00%
Asia/Pacific Fleet
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 4,627	$ 7,921
Percentage of revenue	4.00%	5.00%
Middle East Fleet Deepwater vessels
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 9,547	$ 6,038
Percentage of revenue	9.00%	4.00%
Middle East Fleet Towing-Supply/supply
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 13,592	$ 18,164
Percentage of revenue	12.00%	11.00%
Middle East fleet
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 23,139	$ 24,202
Percentage of revenue	21.00%	15.00%
Africa/Europe Fleet Deepwater vessels
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 22,158	$ 33,289
Percentage of revenue	20.00%	20.00%
Africa/Europe Fleet Towing-Supply/supply
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 27,019	$ 27,917
Percentage of revenue	24.00%	18.00%
Africa And Europe Fleet Other
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 3,427	$ 8,493
Percentage of revenue	3.00%	5.00%
Africa/Europe Fleet
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 52,604	$ 69,699
Percentage of revenue	47.00%	43.00%
Worldwide Fleet Deepwater vessels
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 50,172	$ 82,304
Percentage of revenue	45.00%	51.00%
Worldwide Fleet Towing-Supply/supply
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 55,358	$ 68,291
Percentage of revenue	49.00%	42.00%
Worldwide Fleet Other
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 6,727	$ 11,835
Percentage of revenue	6.00%	7.00%
Worldwide Fleet
Segment and Geographic Distribution of Operations [Line Items]
Vessel revenues	$ 112,257	$ 162,430
Percentage of revenue	100.00%	100.00%