SEGMENT INFORMATION (SEGMENT FINANCIALS) (DETAILS) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Gross Revenue									$ 1,286,987	$ 1,241,817	$ 1,195,553
Intersegment Sales									(232)	(36)	(2,396)
Net Revenue	$ 341,816	$ 309,195	$ 310,223	$ 325,521	$ 338,170	$ 305,900	$ 295,490	$ 302,221	1,286,755	1,241,781	1,193,157
Depreciation and amortization	17,279	15,486	15,680	15,363	15,386	13,893	14,089	13,170	63,808	56,538	46,064
Income (Loss) from Operations	25,075	$ 15,625	$ 23,352	$ 26,128	30,128	$ 21,323	$ 20,667	$ 24,357	90,180	96,475	101,399
Capital Expenditures									66,595	67,641	50,364
Total Assets	843,327				852,475				843,327	852,475	842,342
Goodwill	114,183				128,705				114,183	128,705	102,743
Customer Management Services [Member]
Segment Reporting Information [Line Items]
Gross Revenue									913,272	923,497	892,145
Intersegment Sales									0	0	(1,262)
Net Revenue									913,272	923,497	890,883
Depreciation and amortization									44,633	40,577	33,884
Income (Loss) from Operations									58,018	76,792	75,689
Capital Expenditures									56,570	49,630	40,007
Total Assets	512,100				514,957				512,100	514,957	554,015
Goodwill	22,009				25,871				22,009	25,871	19,819
Customer Growth Services [Member]
Segment Reporting Information [Line Items]
Gross Revenue									129,021	115,434	100,996
Intersegment Sales									0	0	0
Net Revenue									129,021	115,434	100,996
Depreciation and amortization									6,065	6,048	4,127
Income (Loss) from Operations									3,077	7,255	3,024
Capital Expenditures									4,681	3,195	3,421
Total Assets	75,291				88,394				75,291	88,394	86,416
Goodwill	24,439				30,395				24,439	30,395	30,128
Customer Technology Services [Member]
Segment Reporting Information [Line Items]
Gross Revenue									157,838	139,218	152,769
Intersegment Sales									(232)	(36)	(284)
Net Revenue									157,606	139,182	152,485
Depreciation and amortization									9,775	7,489	6,201
Income (Loss) from Operations									13,339	4,519	19,965
Capital Expenditures									4,216	14,423	6,450
Total Assets	159,850				159,441				159,850	159,441	157,040
Goodwill	42,709				42,709				42,709	42,709	42,709
Customer Strategy Services [Member]
Segment Reporting Information [Line Items]
Gross Revenue									86,856	63,668	49,643
Intersegment Sales									0	0	(850)
Net Revenue									86,856	63,668	48,793
Depreciation and amortization									3,335	2,424	1,852
Income (Loss) from Operations									15,746	7,909	2,721
Capital Expenditures									1,128	393	486
Total Assets	96,086				89,683				96,086	89,683	44,871
Goodwill	$ 25,026				$ 29,730				$ 25,026	$ 29,730	$ 10,087