RESTRUCTURING AND INTEGRATION CHARGES AND IMPAIRMENT LOSSES (LIABILITY CLASSIFICATION TABLE) (DETAILS) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restructuring Cost and Reserve [Line Items]
Reduction in force									$ 1,161	$ 3,400	$ 1,814
Facility exit charges									2,219	992
Restructuring charges, net	$ 4,897	$ 6,006	$ 3,593	$ 169	$ 502	$ 3,688	$ 114	$ 88	14,665	4,392	1,814
Customer Management Services
Restructuring Cost and Reserve [Line Items]
Reduction in force									1,012	2,837	1,482
Facility exit charges									2,050	959	0
Customer Growth Services
Restructuring Cost and Reserve [Line Items]
Reduction in force										147	22
Facility exit charges									0	0	0
Customer Technology Services
Restructuring Cost and Reserve [Line Items]
Reduction in force									94	324	13
Facility exit charges									84	33	0
Customer Strategy Services
Restructuring Cost and Reserve [Line Items]
Reduction in force									55	92	297
Facility exit charges									$ 85	$ 0	$ 0