Revenue from Contracts with Customers (ASC 606) - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Net sales	$ 42,984	$ 41,112	$ 128,639	$ 114,606
Mobile connectivity product sales \| Mobile connectivity \| Transferred at point in time
Disaggregation of Revenue [Line Items]
Net sales	6,361	6,671	19,741	18,737
Mobile connectivity product sales \| Mobile connectivity \| Transferred over time
Disaggregation of Revenue [Line Items]
Net sales	490	549	2,047	1,778
Mobile connectivity service \| Mobile connectivity
Disaggregation of Revenue [Line Items]
Net sales	27,537	24,163	76,862	68,950
Inertial navigation product \| Inertial navigation
Disaggregation of Revenue [Line Items]
Net sales	8,388	9,430	29,152	23,178
Inertial navigation service \| Inertial navigation
Disaggregation of Revenue [Line Items]
Net sales	$ 208	$ 299	$ 837	$ 1,963

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration