REVENUE RECOGNITION AND RECEIVABLES - Timing of Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
REVENUE RECOGNITION AND RECEIVABLES
Total revenue	$ 172,908	$ 172,557
Operating lease income	2,106	1,903
Government grant revenue	11,780	11,314
Total revenue	186,794	185,774
Services transferred over time
REVENUE RECOGNITION AND RECEIVABLES
Total revenue	166,603	166,752
Goods and services transferred at a point in time
REVENUE RECOGNITION AND RECEIVABLES
Total revenue	6,305	5,805
International Telecom
REVENUE RECOGNITION AND RECEIVABLES
Total revenue	91,594	88,939
Operating lease income	72	72
Government grant revenue	1,393	1,397
Total revenue	93,059	90,408
International Telecom | Services transferred over time
REVENUE RECOGNITION AND RECEIVABLES
Total revenue	88,560	85,680
International Telecom | Goods and services transferred at a point in time
REVENUE RECOGNITION AND RECEIVABLES
Total revenue	3,034	3,259
US Telecom
REVENUE RECOGNITION AND RECEIVABLES
Total revenue	81,314	83,618
Operating lease income	2,034	1,831
Government grant revenue	10,387	9,917
Total revenue	93,735	95,366
US Telecom | Services transferred over time
REVENUE RECOGNITION AND RECEIVABLES
Total revenue	78,043	81,072
US Telecom | Goods and services transferred at a point in time
REVENUE RECOGNITION AND RECEIVABLES
Total revenue	$ 3,271	$ 2,546