Segment Reporting - Net Sales and Operating Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Net sales	$ 42,984	$ 41,112	$ 128,639	$ 114,606
Loss from operations	(3,229)	(503)	(12,638)	(11,587)
Net interest and other income (expense)	7,263	(143)	6,896	1,721
Income (loss) before income tax expense (benefit)	4,034	(646)	(5,742)	(9,866)
Operating Segments
Segment Reporting Information [Line Items]
Loss from operations	1,859	3,693	4,777	1,311
Operating Segments | Mobile connectivity
Segment Reporting Information [Line Items]
Net sales	34,388	31,383	98,650	89,465
Loss from operations	1,545	2,285	1,728	570
Operating Segments | Inertial navigation
Segment Reporting Information [Line Items]
Net sales	8,596	9,729	29,989	25,141
Loss from operations	314	1,408	3,049	741
Unallocated
Segment Reporting Information [Line Items]
Loss from operations	$ (5,088)	$ (4,196)	$ (17,415)	$ (12,898)