ACQUISITIONS AND DIVESTITURES (NARRATIVE) (DETAILS) CAD in Millions				3 Months Ended								6 Months Ended	7 Months Ended
	Jun. 30, 2017 USD ($)	Apr. 03, 2017 USD ($)	Nov. 09, 2016 CAD	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Dec. 31, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Jun. 30, 2017 USD ($)	Aug. 08, 2014 USD ($)	Nov. 09, 2016 USD ($)
Business Acquisition [Line Items]
Contingent Consideration, at fair value	$ 1,393,000			$ 1,393,000		$ 1,808,000						$ 1,393,000
Loss on assets held-for-sale				3,178,000								3,178,000
Investments in non-marketable equity investments												1,384,000
Customer Growth Services | Business unit 1 [Member]
Business Acquisition [Line Items]
Loss on assets held-for-sale							$ 2,600,000
Customer Strategy Services | Business unit 2 [Member]
Business Acquisition [Line Items]
Loss on assets held-for-sale							2,700,000
Connextions [Member]
Business Acquisition [Line Items]
Description of Acquired Entity		Connextions, Inc., a health care customer service provider company, from OptumHealth Holdings, LLC. Connextions is being integrated into the health care vertical of the Customer Management Services ("CMS") segment of the Company. Connextions employed approximately 2,000 at several centers in the U.S.
Total purchase price		$ 77,712,000
Connextions [Member] | Customer Relationships [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life		12 years
Atelka [Member]
Business Acquisition [Line Items]
Description of Acquired Entity			On November 9, 2016, the Company acquired all of the outstanding shares of Atelka Enterprise Inc. ("Atelka"), a Canadian customer contact center management and business process outsourcing services company that serves Canadian telecommunications, logistics, and entertainment clients. This acquisition is an addition to the CMS segment. Atelka employed approximately 2,800 in Quebec, Ontario, New Brunswick and Prince Edward Island.
Total purchase price														$ 48,401,000
Cost of Acquired Entity, Up Front Cash Consideration														47,500,000
Acquisition hold-back payment														$ 1,400,000
Discount rate	0.00%
Contingent Consideration, at fair value	$ 578,000			578,000		558,000						$ 578,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life			12 years
Atelka [Member] | CAD
Business Acquisition [Line Items]
Total purchase price | CAD			CAD 65.0
rogenSi [Member]
Business Acquisition [Line Items]
Description of Acquired Entity													rogenSi Worldwide PTY, Ltd., a global leadership, change management, sales, performance training and consulting company.
Total purchase price													$ 34,400,000
Cost of Acquired Entity, Up Front Cash Consideration													18,100,000
Future Value of Liabilities Incurred From Business Acquisitions													$ 15,300,000
Valuation Technique on Contingent Consideration													The fair value of the contingent consideration was measured by applying a probability weighted discounted cash flow model based on significant inputs not observable in the market (Level 3 inputs). Key assumptions include a discount rate of 4.6% and expected future value of payments of $15.3 million. The $15.3 million of expected future payments was calculated using a probability weighted EBITDA assessment with the highest probability associated with rogenSi achieving the targeted EBITDA for each earn-out year
Acquisition hold-back payment													$ 1,800,000
Discount rate													4.60%
Contingent Consideration Arrangements, Basis for Amount													The total contingent consideration possible per the sale and purchase agreement ranged from zero to $17.6 million and the earn-out payments were payable in early 2015, 2016 and 2017, based on July 1, 2014 through December 31, 2014, and full year 2015 and 2016 performance, respectively. As of December 31, 2016, the contingent consideration has been finalized and a total of $12.0 million was earned and paid
Contingent Consideration, at fair value							$ 4,300,000						$ 14,500,000
Contingent Consideration, at Fair Value, Current Portion						0
Increase (decrease) in contingent consideration payable				$ (4,300,000)				$ 800,000	$ (300,000)		$ 500,000
CafeX [Member]
Business Acquisition [Line Items]
Equity Method Investment, Ownership Percentage	17.20%			17.20%					17.20%			17.20%
Investments in non-marketable equity investments					$ 1,100,000	$ 3,200,000				$ 9,000,000