Summary of Significant Accounting Policies - Inventories (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Mar. 31, 2016
Inventories
Raw material and components, cost	$ 9,356	$ 10,556
Raw material and components, obsolescence reserve	(1,279)	(1,052)
Raw material and components, net	8,077	9,504
Work in process, cost	1,280	2,045
Work in process, obsolescence reserve	(136)	(119)
Work in process, net	1,144	1,926
Finished goods, cost	8,941	6,550
Finished goods, obsolescence reserve	(1,155)	(956)
Finished goods, net	7,786	5,594
Cost	19,577	19,151
Obsolescence reserve	(2,570)	(2,127)
Net	$ 17,007	$ 17,024