RELATED PARTY TRANSACTIONS (NARRATIVE) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Related Party Transaction Line Items
Sales Revenue Services Net	$ 570,974	$ 492,980	$ 453,081	$ 432,213	$ 461,326	$ 395,507	$ 392,515	$ 394,356	$ 1,949,248	$ 1,643,704	$ 1,509,171
Airmax [Member]
Related Party Transaction Line Items
Purchases from Related Party									400	1,100	1,100
Accounts Payable Due from Related Party	$ 67								67
CafeX [Member]
Related Party Transaction Line Items
Purchases from Related Party									$ 0	50	61
Equity Method Investment, Ownership Percentage	17.80%								17.80%
Welltok
Related Party Transaction Line Items
Sales Revenue Services Net									$ 3,000	$ 5,300	$ 5,700