REVENUE RECOGNITION AND RECEIVABLES - Timing of Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
REVENUE RECOGNITION AND RECEIVABLES
Total revenue	$ 164,602	$ 177,979	$ 506,876	$ 523,975
Operating lease income	2,075	1,948	6,293	5,810
Government grant revenue	11,774	11,109	35,358	33,465
Total revenue	178,451	191,036	548,527	563,250
Services transferred over time
REVENUE RECOGNITION AND RECEIVABLES
Total revenue	158,995	169,116	487,698	502,928
Good and services transferred at point in time
REVENUE RECOGNITION AND RECEIVABLES
Total revenue	5,607	8,863	19,178	21,047
International Telecom
REVENUE RECOGNITION AND RECEIVABLES
Total revenue	92,730	92,409	278,213	271,858
Operating lease income	157	72	304	217
Government grant revenue	1,394	1,397	4,180	4,192
Total revenue	94,281	93,878	282,697	276,267
International Telecom | Services transferred over time
REVENUE RECOGNITION AND RECEIVABLES
Total revenue	89,139	87,657	267,970	260,066
International Telecom | Good and services transferred at point in time
REVENUE RECOGNITION AND RECEIVABLES
Total revenue	3,591	4,752	10,243	11,792
US Telecom
REVENUE RECOGNITION AND RECEIVABLES
Total revenue	71,872	85,570	228,663	252,117
Operating lease income	1,918	1,876	5,989	5,593
Government grant revenue	10,380	9,712	31,178	29,273
Total revenue	84,170	97,158	265,830	286,983
US Telecom | Services transferred over time
REVENUE RECOGNITION AND RECEIVABLES
Total revenue	69,856	81,459	219,728	242,862
US Telecom | Good and services transferred at point in time
REVENUE RECOGNITION AND RECEIVABLES
Total revenue	$ 2,016	$ 4,111	$ 8,935	$ 9,255