PROPERTY AND EQUIPMENT (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Mar. 31, 2012
Property, Plant and Equipment [Line Items]
Cost	$ 262,309	$ 245,911
Accumulated depreciation	45,560	45,049
Property and equipment, net	216,749	200,862
Acquired vessel included in property and equipment not yet in use	37,773	21,927
Vessels [Member]
Property, Plant and Equipment [Line Items]
Cost	255,264	238,830
Accumulated depreciation	42,510	42,426
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Cost	3,782	3,847
Accumulated depreciation	1,266	1,034
Furniture and equipment [Member]
Property, Plant and Equipment [Line Items]
Cost	339	335
Accumulated depreciation	182	162
Vehicles [Member]
Property, Plant and Equipment [Line Items]
Cost	23	21
Accumulated depreciation	13	12
Computer, communication equipment and purchased software [Member]
Property, Plant and Equipment [Line Items]
Cost	2,901	2,878
Accumulated depreciation	$ 1,589	$ 1,415