Segment Reporting Depreciation and Amortization Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Depreciation	$ 6,725	$ 7,608	$ 7,193
Amortization expense	4,312	4,956	5,526
Other Segments [Member]
Segment Reporting Information [Line Items]
Depreciation	77	461	389
Amortization expense	0	0	0
Mobile Connectivity [Member]
Segment Reporting Information [Line Items]
Depreciation	5,720	6,084	5,843
Amortization expense	4,312	4,956	5,526
Intertial Navigation [Member]
Segment Reporting Information [Line Items]
Depreciation	928	1,063	961
Amortization expense	$ 0	$ 0	$ 0