Supplementary Financial Information - Intangible Assets (Details) - USD ($)	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Intangible Assets
Gross Carrying Amount	$ 8,824,000	$ 5,874,000
Accumulated Amortization	(5,073,000)	(4,376,000)
Amortization expense	726,000	623,000	$ 526,000
Amortization recorded to cost of revenues	638,000	342,000	166,000
Amortization of intangible assets	88,000	281,000	$ 360,000
Net capitalized software development costs	3,800,000
Future estimated amortization expense
Net Book Value	3,751,000	1,498,000
Agriculture and Weather Analytics
Future estimated amortization expense
2019	1,076,000
2020	807,000
2021	339,000
2022	244,000
2023	244,000
Thereafter	1,041,000
Net Book Value	$ 3,751,000
Agriculture and Weather Analytics and Roadway Sensors Segments
Intangible Assets
Useful life (in years)	3 years
Technology
Intangible Assets
Gross Carrying Amount	$ 1,856,000	1,856,000
Accumulated Amortization	(1,856,000)	(1,828,000)
Customer contracts / relationships
Intangible Assets
Gross Carrying Amount	750,000	750,000
Accumulated Amortization	(750,000)	(726,000)
Trade names and non-compete agreements
Intangible Assets
Gross Carrying Amount	1,110,000	1,110,000
Accumulated Amortization	(1,102,000)	(1,066,000)
Capitalized software development costs
Intangible Assets
Gross Carrying Amount	5,108,000	2,158,000
Accumulated Amortization	(1,365,000)	$ (756,000)
Oracle ERP development
Intangible Assets
Net capitalized software development costs	$ 2,300,000
Useful life (in years)	10 years