GOODWILL (NARRATIVE) (DETAILS) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
	Dec. 31, 2017	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	Dec. 01, 2017
ValuationAllowanceForImpairmentOfRecognizedServicingAssetsLineItems
Goodwill	$ 206,694	$ 206,694				$ 129,648				$ 206,694	$ 129,648	$ 114,183
Goodwill, Impaired, Method for Fair Value Determination	The process of evaluating the fair value of the reporting units is highly subjective and requires significant judgment and estimates as the reporting units operate in a number of markets and geographical regions. We used a market approach and an income approach to determine our best estimates of fair value which incorporated the following significant assumptions:Revenue projections, including revenue growth during the forecast periods ranging from (3.2)% to 7.8%;EBITDA margin projections held relatively flat over the forecast periods ranging from 10% to 21.4%;Estimated income tax rates of 14.6% to 34.3%;Estimated capital expenditures ranging from $0.8 million to $40.4 million; andDiscount rates ranging from 10% to 16% based on various inputs, including the risks associated with the specific reporting units, the country of operations as well as their revenue growth and EBITDA margin assumptions.
Impairment losses		5,322	$ 0	$ 0	$ 0	26,448	$ 5,602	$ 0	$ 0	5,322	32,050	8,100
Customer Management Services
ValuationAllowanceForImpairmentOfRecognizedServicingAssetsLineItems
Goodwill	$ 119,497	119,497				42,589				119,497	42,589	23,218
Customer Strategy Services
ValuationAllowanceForImpairmentOfRecognizedServicingAssetsLineItems
Goodwill	21,919	21,919				21,120				21,919	21,120	25,026	$ 22,000
Fair value of a reporting unit in excess of carrying value expressed as a percentage													44.00%
Customer Growth Services
ValuationAllowanceForImpairmentOfRecognizedServicingAssetsLineItems
Goodwill	24,439	24,439				24,439				24,439	24,439	24,439
Customer Technology Services
ValuationAllowanceForImpairmentOfRecognizedServicingAssetsLineItems
Goodwill	$ 40,839	$ 40,839				41,500				$ 40,839	$ 41,500	$ 41,500
Humanify - reporting unit | Customer Management Services
ValuationAllowanceForImpairmentOfRecognizedServicingAssetsLineItems
Goodwill, Impaired, Method for Fair Value Determination	For the goodwill impairment analysis, the Company calculated the fair value of the Humanify reporting unit and compared that to the updated carrying value and determined that the fair value was not in excess of its carrying value. Key assumptions used in the fair value calculation for goodwill impairment testing include, but are not limited to, revenue growth of approximately $300 thousand to $1 million per year through 2027, a perpetual growth rate of 3%, a discount rate of 16.75%, and negative EBITDA through 2020 growing to a 15.6% EBITDA for the terminal year
Humanify - reporting unit | Customer Management Services | Other Intangible Assets
ValuationAllowanceForImpairmentOfRecognizedServicingAssetsLineItems
Impairment losses						$ 10,800