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RESTRUCTURING AND INTEGRATION CHARGES AND IMPAIRMENT LOSSES (NARRATIVE) (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Reduction in force		$ 347			$ 800	$ 907
Restructuring Reserve, Period Increase (Decrease)					500
Facility exit charges	$ 485	886			1,812	1,657
Restructuring reserve decrease
Restructuring Reserve, Period Increase (Decrease)					600
Leasehold Improvements
Restructuring impairment losses		900			400	1,600
TTEC Digital
Reduction in force		347			858	668
Facility exit charges	2	90			10	90
TTEC Engage
Reduction in force					(58)	239
Facility exit charges	483	$ 796			$ 1,802	$ 1,567
TTEC Engage \| Leasehold Improvements
Restructuring impairment losses	$ (300)
Cost of Services
Restructuring Reserve, Period Increase (Decrease)			$ 3,000	$ 300
Cost of Services \| Restructuring reserve decrease
Restructuring Reserve, Period Increase (Decrease)				$ (1,600)