Property, Plant and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Mar. 31, 2018
Property, Plant and Equipment
Total property, plant and equipment, gross	$ 28,966		$ 29,334
Less, accumulated depreciation	(26,178)		(26,475)
Total property, plant and equipment, net	2,788		2,859
Depreciation expense	200	$ 200
Machinery, rental equipment, equipment, automobiles and furniture
Property, Plant and Equipment
Total property, plant and equipment, gross	15,115		15,481
Leasehold improvements
Property, Plant and Equipment
Total property, plant and equipment, gross	11,017		10,949
Molds and tooling
Property, Plant and Equipment
Total property, plant and equipment, gross	$ 2,834		$ 2,904