Business Segments, Significant Customer and Geographic Information - Business segments (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2017 USD ($) segment	Mar. 31, 2016 USD ($)	Mar. 31, 2015 USD ($)
Business Segments
Number of reportable segments | segment									3
Revenues	$ 25,304	$ 22,691	$ 24,060	$ 23,927	$ 19,796	$ 19,014	$ 20,573	$ 18,365	$ 95,982	$ 77,748	$ 72,251
Depreciation									729	649	525
Loss on impairment of goodwill									2,168
Segment income (loss)									(5,237)	(3,470)	(2,079)
Operating segments
Business Segments
Revenues									95,982	77,748	72,251
Depreciation									502	449	376
Loss on impairment of goodwill									2,168
Segment income (loss)									8,724	6,431	7,638
Operating segments | Roadway Sensors
Business Segments
Revenues									42,170	40,259	36,370
Depreciation									180	152	119
Segment income (loss)									9,799	8,401	6,840
Operating segments | Transportation Systems
Business Segments
Revenues									49,270	34,096	32,832
Depreciation									191	175	151
Segment income (loss)									8,482	4,170	3,620
Operating segments | Agriculture and Weather Analytics
Business Segments
Revenues									4,542	3,393	3,049
Depreciation									131	122	106
Loss on impairment of goodwill									2,168
Segment income (loss)									$ (9,557)	$ (6,140)	$ (2,822)