PROPERTY AND EQUIPMENT, NET (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Mar. 31, 2017
Property, Plant and Equipment [Line Items]
Cost	$ 351,715	$ 327,302
Accumulated depreciation	128,470	113,256
Property and equipment, net	223,245	214,046
Vessels
Property, Plant and Equipment [Line Items]
Cost	346,627	322,820
Accumulated depreciation	125,241	110,338
Leasehold improvements
Property, Plant and Equipment [Line Items]
Cost	186	146
Accumulated depreciation	79	61
Furniture and equipment
Property, Plant and Equipment [Line Items]
Cost	624	594
Accumulated depreciation	463	408
Vehicles
Property, Plant and Equipment [Line Items]
Cost	12	15
Accumulated depreciation	12	13
Computer, communication equipment and purchased software
Property, Plant and Equipment [Line Items]
Cost	4,266	3,727
Accumulated depreciation	$ 2,675	$ 2,436