Sale of Vehicle Sensors (Details) (Vehicle Sensors segment, USD $)	0 Months Ended	1 Months Ended	3 Months Ended	9 Months Ended	18 Months Ended
	Jul. 25, 2011	Jul. 31, 2011	Dec. 31, 2012	Dec. 31, 2012	Dec. 31, 2012
Vehicle Sensors segment
Sale of Vehicle Sensors
Aggregate proceeds received on sale	$ 14,000,000
Additional cash consideration, percentage of revenue associated with royalties		85.00%
Additional cash consideration, percentage on excess of revenue over projected revenue		30.00%
Additional cash consideration, period for which revenue generated exceeds target revenue		2 years
Amount of earn-out, net of tax			388,000	475,000	604,000
Gain on the sale related to performance and royalty-related earn-outs achieved, net of tax			1,400,000	1,500,000
Holdback amount	$ 2,000,000