Revenue from Contracts with Customers (ASC 606) - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net sales	$ 36,568	$ 36,376
Product
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net sales	13,094	13,215
Product | Intertial Navigation
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net sales	6,502	5,812
Service
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net sales	23,474	23,161
Service | Mobile Connectivity
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net sales	22,304	21,511
Service | Intertial Navigation
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net sales	1,170	1,650
Transferred at Point in Time | Product | Mobile Connectivity
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net sales	5,986	6,922
Transferred over Time | Product | Mobile Connectivity
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net sales	$ 606	$ 481