ACQUISITIONS AND DIVESTITURES (NARRATIVE) (DETAILS) CAD in Millions					3 Months Ended								7 Months Ended	9 Months Ended
	Nov. 08, 2017 USD ($)	Sep. 30, 2017 USD ($)	Apr. 03, 2017 USD ($)	Nov. 09, 2016 CAD	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Dec. 31, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Aug. 08, 2014 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Nov. 09, 2016 USD ($)
Business Acquisition [Line Items]
Cost of Acquired Entity, Up Front Cash Consideration			$ 80,000,000
Contingent Consideration, at fair value		$ 1,178,000			$ 1,178,000			$ 1,808,000						$ 1,178,000
Revenue of Acquirees since Acquisition Date, Actual					43,600,000									101,900,000
Income (loss) from operations of Acquirees since Acquisition Date, Actual					(4,100,000)									(6,300,000)
Proceeds from sale of business														391,000
Gain on sale of business														3,323,000
Other nonoperating income expense					(4,416,000)				$ (6,254,000)					(6,573,000)	$ (7,488,000)
Business Combination Pro Forma Information Amortization Expense of Acquirees Since Acquisition					900,000									2,100,000
Business Acquisition, Pro Forma Revenue					359,000,000				362,300,000					1,090,000,000	1,071,700,000
Business Acquisition, Pro Forma Income (Loss) from Continuing Operations, Net of Tax					14,800,000				9,400,000					46,900,000	27,800,000
Investments in non-marketable equity investments														1,384,000
Technology Solutions Group
Business Acquisition [Line Items]
Proceeds from sale of business					141,000	$ 250,000
Gain on sale of business						$ 30,000
TeleTech Spain Holdings SL [Member]
Business Acquisition [Line Items]
Other nonoperating income expense					3,200,000
Connextions [Member]
Business Acquisition [Line Items]
Total purchase price			$ 77,712,000
Payments for Previous Acquisition					1,800,000
Proceeds from Previous Acquisition					4,100,000
Connextions [Member] | Customer Management Services
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.
Connextions [Member] | Customer Relationships
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 was 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		$ 602,000			602,000			558,000						$ 602,000
Atelka [Member] | CAD
Business Acquisition [Line Items]
Total purchase price | CAD				CAD 65.0
Atelka [Member] | Customer Relationships
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life				12 years
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		$ 4,300,000
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
Motif [Member]
Business Acquisition [Line Items]
Percentage of Voting Interests Acquired	70.00%
Description of Acquired Entity	Motif, Inc., a California corporation ("Motif"). Motif is a digital trust and safety services company serving eCommerce marketplaces, online retailers, travel agencies and financial services companies. Motif provides omni-channel community moderation services via voice, email and chat from delivery centers in India and the Philippines via approximately 2,800 employees
Total purchase price	$ 46,900,000
Contingent Consideration Arrangements, Basis for Amount	The Company also agreed to purchase the remaining 30% interest in Motif from Motif's founders ("founders' shares") by no later than May 2020 ("30% buyout period"). The Company agreed to pay for the founders' shares at a purchase price contingent on Motif's fiscal year 2020's adjusted normalized EBITDA, and 30% of the excess cash present in the business at the time of the buyout; or if the buyout occurs prior to May 2020, the trailing twelve months EBITDA, calculated from the most recently completed full monthly period ending prior to the date of the buyout triggering event and 30% of the excess cash in the business at that point.