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RELATED PARTY TRANSACTIONS (NARRATIVE) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Related Party Transaction Line Items
Sales Revenue Services Net	$ 461,326	$ 395,507	$ 392,515	$ 394,356	$ 419,133	$ 364,936	$ 349,853	$ 375,249	$ 1,643,704	$ 1,509,171	$ 1,477,365
Airmax [Member]
Related Party Transaction Line Items
Purchases from Related Party									1,100	1,100	1,100
Accounts Payable Due from Related Party	$ 200								200
Convercent [Member]
Related Party Transaction Line Items
Purchases from Related Party									60	60	70
CafeX [Member]
Related Party Transaction Line Items
Purchases from Related Party									50	61	72
Welltok
Related Party Transaction Line Items
Sales Revenue Services Net									$ 5,300	$ 5,700	$ 5,500