Revenue Recognition - Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Total revenue	$ 22,174	$ 19,774	$ 43,363	$ 39,014
Product, accessories and parts
Disaggregation of Revenue [Line Items]
Total revenue	18,627	16,005	35,712	31,496
Total from Micro turbine Products
Disaggregation of Revenue [Line Items]
Total revenue	14,876		28,509
Accessories and parts
Disaggregation of Revenue [Line Items]
Total revenue	3,751		7,203
Service
Disaggregation of Revenue [Line Items]
Total revenue	3,547	$ 3,769	7,651	$ 7,518
Total North America
Disaggregation of Revenue [Line Items]
Total revenue	12,275		23,874
United States
Disaggregation of Revenue [Line Items]
Total revenue	10,938		21,812
Mexico
Disaggregation of Revenue [Line Items]
Total revenue	1,186		1,795
All other North America
Disaggregation of Revenue [Line Items]
Total revenue	151		267
Europe
Disaggregation of Revenue [Line Items]
Total revenue	3,689		6,651
United Kingdom
Disaggregation of Revenue [Line Items]
Total revenue	648		2,559
Columbia
Disaggregation of Revenue [Line Items]
Total revenue	43		2,659
Asia
Disaggregation of Revenue [Line Items]
Total revenue	2,212		3,066
Australia
Disaggregation of Revenue [Line Items]
Total revenue	512		1,365
Kuwait
Disaggregation of Revenue [Line Items]
Total revenue	2,161		2,161
All other
Disaggregation of Revenue [Line Items]
Total revenue	$ 634		$ 1,028