Segment Reporting Segments - Net Sales and Operating Earnings (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Revenue, Net									$ 160,088	$ 176,122	$ 184,634
Operating Income (Loss)	$ (1,125)	$ (1,801)	$ (1,368)	$ (4,470)	$ (268)	$ 3,013	$ (693)	$ (3,374)	(8,764)	(1,322)	3,208
Net interest and other expense									(1,174)	(648)	(542)
(Loss) income before income tax expense									(9,938)	(1,970)	2,666
Mobile Connectivity and Intertial Navigation Combined [Member]
Segment Reporting Information [Line Items]
Operating Income (Loss)									7,890	15,313	17,393
Other Segments [Member]
Segment Reporting Information [Line Items]
Operating Income (Loss)									(16,654)	(16,635)	(14,185)
Operating Segments [Member] | Mobile Connectivity [Member]
Segment Reporting Information [Line Items]
Revenue, Net									132,227	141,507	147,809
Operating Income (Loss)									7,334	10,041	9,459
Operating Segments [Member] | Intertial Navigation [Member]
Segment Reporting Information [Line Items]
Revenue, Net									27,861	34,615	36,825
Operating Income (Loss)									$ 556	$ 5,272	$ 7,934