ACQUISITIONS AND DIVESTITURES (NARRATIVE) (Details) £ in Millions								3 Months Ended								6 Months Ended
	Apr. 30, 2018 GBP (£)	Apr. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 22, 2017 USD ($)	Nov. 08, 2017 USD ($)	Apr. 03, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Mar. 31, 2015 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Apr. 30, 2018 USD ($)	Dec. 31, 2015
Business Acquisition [Line Items]
Other liabilities, noncurrent								$ 101,208,000		$ 95,243,000						$ 101,208,000
Contingent Consideration, at fair value								2,746,000		399,000						2,746,000
Revenue of Acquirees since Acquisition Date, Actual								37,400,000								88,400,000
Income (loss) from operations of Acquirees since Acquisition Date, Actual								1,200,000								9,000,000
Proceeds from sale of business																	$ 250,000
Non-cash loss on assets held-for-sale								2,000,000				$ 3,178,000				2,000,000	3,178,000
Gain on sale of business																	30,000
Impairment losses																1,120,000
Acquired intangible amortization of acquirees since acquisition								1,600,000								3,300,000
Business Acquisition, Pro Forma Revenue								350,100,000				364,500,000				729,400,000	753,300,000
Business Acquisition, Pro Forma Income (Loss) from Continuing Operations, Net of Tax								5,600,000				16,800,000				10,700,000	36,300,000
Investments in non-marketable equity investments																2,119,000	1,384,000
Other nonoperating income expense								1,741,000				1,197,000				(9,775,000)	$ 2,157,000
Technology Solutions Group [Member]
Business Acquisition [Line Items]
Proceeds from sale of business											$ 141,000	250,000
Gain on sale of business												30,000
Impairment losses												$ 700,000
Other nonoperating income expense								271,000	$ 794,000	259,000
TeleTech Spain Holdings SL [Member]
Business Acquisition [Line Items]
Other nonoperating income expense											3,200,000
Customer Growth Services [Member]
Business Acquisition [Line Items]
Proceeds from sale of business				$ 245,000						$ 600,000
Non-cash loss on assets held-for-sale							$ 2,600,000
Customer Strategy Services [Member]
Business Acquisition [Line Items]
Non-cash loss on assets held-for-sale							$ 2,700,000
SCS
Business Acquisition [Line Items]
Description of Acquired Entity	Strategic Communications ServicesOn April 30, 2018, the Company acquired all of the outstanding equity securities of Strategic Communications Services, Ltd ("SCS"). SCS provides services as a system integrator for multichannel contact center platforms, including CISCO. The Company offers in-house, managed and outsourced network, information, communications and contact center services to leading brands throughout Europe. This business will be integrated into the Company's CTS segment.	Strategic Communications ServicesOn April 30, 2018, the Company acquired all of the outstanding equity securities of Strategic Communications Services, Ltd ("SCS"). SCS provides services as a system integrator for multichannel contact center platforms, including CISCO. The Company offers in-house, managed and outsourced network, information, communications and contact center services to leading brands throughout Europe. This business will be integrated into the Company's CTS segment.
Payments to Acquire Businesses	£ 4.4	$ 6,100,000
Cash																		$ 4,509,000
Total purchase price																		9,193,000
Contingent Consideration, at fair value								$ 2,746,000								2,746,000		4,100,000
SCS | United Kingdom, Pounds
Business Acquisition [Line Items]
Cash																		$ 4,500,000
Contingent Consideration, at Fair Value, Current Portion | £	£ 3.0
BH
Business Acquisition [Line Items]
Date of Acquisition			Mar. 31, 2018
Description of Acquired Entity			Berkshire Hathaway Specialty ConciergeOn March 31, 2018, the Company, through its subsidiary Percepta, acquired certain assets from Berkshire Hathaway Specialty Concierge, LLC ("BH") related to a customer engagement center and the related customer contracts. This acquisition is being accounted for as a business combination. These assets will be integrated into the Company's CMS segment.
Total purchase price			$ 1						1
BH | Customer Relationships [Member]
Business Acquisition [Line Items]
Fair Value of Assets Acquired			257,000
BH | Lease Agreements [Member]
Business Acquisition [Line Items]
Fair Value of Assets Acquired			330,000
BH | Fixed Assets
Business Acquisition [Line Items]
Fair Value of Assets Acquired			98,000
Motif [Member]
Business Acquisition [Line Items]
Date of Acquisition					Nov. 08, 2017
Percentage of Voting Interests Acquired					70.00%
Description of Acquired Entity					MotifOn November 8, 2017, the Company agreed to acquire all of the outstanding shares in 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 2,700 employees. Motif will be integrated into the Company's CMS segment.
Payments to Acquire Businesses					$ 46,800,000
Cash					5,997,000
Total purchase price					$ 73,438,000
Other liabilities, noncurrent			$ 32,800,000						$ 32,800,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life					11 years
Connextions
Business Acquisition [Line Items]
Date of Acquisition						Apr. 03, 2017
Total purchase price						$ 77,712,000
Payments for Previous Acquisition											$ 1,800,000
Proceeds from Previous Acquisition																$ 4,100,000
Cost of Acquired Entity, Up Front Cash Consideration						$ 80,000,000
Connextions | Customer Management Services [Member]
Business Acquisition [Line Items]
Description of Acquired Entity						Connextions, Inc., a health care customer service provider company, from OptumHealth Holdings, LLC. Connextions has been integrated into the health care vertical of the CMS segment of the Company. Connextions employed approximately 2,000 at several centers in the U.S.
Connextions | Customer Relationships [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life						12 years
CafeX [Member]
Business Acquisition [Line Items]
Equity Method Investment, Ownership Percentage			17.20%						17.20%										17.20%
Investments in non-marketable equity investments													$ 1,100,000	$ 3,200,000	$ 9,000,000
Bridge Loan			$ 2,100,000						$ 2,100,000
Bridge loan stated interest rate			12.00%						12.00%