Property, Plant and Equipment - Schedule of Costs and Accumulated Depreciation (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Mar. 31, 2018
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 76,516	$ 76,718
Less accumulated depreciation	(64,962)	(64,205)
Property, plant and equipment, net	11,554	12,513
Construction in progress - equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	528	654
Equipment and software
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	72,466	72,760
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,890	1,878
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 1,632	$ 1,426