Geographic Information - Information by Geographic Area Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Segment Reporting Information [Line Items]
Service revenues	$ 19,644	$ 18,511	$ 55,367	$ 52,647
Subscriber equipment revenues	4,034	4,930	12,356	15,324
Total revenue	23,678	23,441	67,723	67,971
United States
Segment Reporting Information [Line Items]
Service revenues	13,506	12,267	37,689	35,000
Subscriber equipment revenues	2,304	2,510	5,883	8,340
Canada
Segment Reporting Information [Line Items]
Service revenues	3,863	4,077	11,067	10,946
Subscriber equipment revenues	962	1,418	3,401	4,187
Europe
Segment Reporting Information [Line Items]
Service revenues	1,634	1,655	4,377	4,407
Subscriber equipment revenues	313	540	1,299	1,628
Central and South America
Segment Reporting Information [Line Items]
Service revenues	486	440	1,788	1,886
Subscriber equipment revenues	409	437	1,465	930
Others
Segment Reporting Information [Line Items]
Service revenues	155	72	446	408
Subscriber equipment revenues	$ 46	$ 25	$ 308	$ 239