Segment Reporting Segments - Net Sales and Operating Earnings (Details) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Revenue, Net					$ 176,122	$ 184,634	$ 172,591
Operating Income (Loss)	$ (268)	$ 3,013	$ (693)	$ (3,374)	(1,322)	3,208	1,922
Net interest and other expense					(648)	(542)	(597)
(Loss) income before income tax expense					(1,970)	2,666	1,325
Mobile Connectivity and Intertial Navigation Combined [Member]
Segment Reporting Information [Line Items]
Operating Income (Loss)					15,313	17,393	15,487
Other Segments [Member]
Segment Reporting Information [Line Items]
Operating Income (Loss)					(16,635)	(14,185)	(13,565)
Operating Segments [Member] | Mobile Connectivity [Member]
Segment Reporting Information [Line Items]
Revenue, Net					141,507	147,809	129,819
Operating Income (Loss)					10,041	9,459	5,056
Operating Segments [Member] | Intertial Navigation [Member]
Segment Reporting Information [Line Items]
Revenue, Net					34,615	36,825	42,772
Operating Income (Loss)					$ 5,272	$ 7,934	$ 10,431