SEGMENT INFORMATION (SEGMENT FINANCIALS) (DETAILS) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	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
Segment Reporting Information [Line Items]
Net Revenue	$ 426,623	$ 359,036	$ 353,429	$ 338,277	$ 344,947	$ 312,796	$ 305,105	$ 312,410	$ 1,477,365	$ 1,275,258	$ 1,286,755
Depreciation and amortization	17,234	16,515	16,258	14,500	16,914	16,811	17,221	17,729	64,507	68,675	63,808
Income (Loss) from Operations	36,610	$ 15,800	$ 21,589	$ 26,490	6,245	$ 12,526	$ 16,228	$ 17,753	100,489	52,752	90,180
Capital Expenditures									51,958	50,832	66,595
Total Assets	1,078,736				846,304				1,078,736	846,304	843,327
Goodwill	206,694				129,648				206,694	129,648	114,183
Operating Segments
Segment Reporting Information [Line Items]
Net Revenue									1,477,721	1,276,198	1,286,987
Intersegment Eliminations
Segment Reporting Information [Line Items]
Net Revenue									(356)	(940)	(232)
Customer Management Services
Segment Reporting Information [Line Items]
Net Revenue									1,141,760	924,325	913,272
Depreciation and amortization									52,193	48,770	44,633
Income (Loss) from Operations									78,206	50,541	58,018
Capital Expenditures									48,069	40,321	56,570
Total Assets	869,594				585,679				869,594	585,679	525,470
Goodwill	119,497				42,589				119,497	42,589	23,218
Customer Management Services | Operating Segments
Segment Reporting Information [Line Items]
Net Revenue									1,141,779	924,654	913,272
Customer Management Services | Intersegment Eliminations
Segment Reporting Information [Line Items]
Net Revenue									(19)	(329)	0
Customer Growth Services
Segment Reporting Information [Line Items]
Net Revenue									128,698	141,005	129,021
Depreciation and amortization									2,959	5,905	6,065
Income (Loss) from Operations									7,803	6,969	3,077
Capital Expenditures									871	4,185	4,681
Total Assets	41,036				71,540				41,036	71,540	75,291
Goodwill	24,439				24,439				24,439	24,439	24,439
Customer Growth Services | Operating Segments
Segment Reporting Information [Line Items]
Net Revenue									128,698	141,005	129,021
Customer Growth Services | Intersegment Eliminations
Segment Reporting Information [Line Items]
Net Revenue									0	0	0
Customer Technology Services
Segment Reporting Information [Line Items]
Net Revenue									138,581	141,254	157,606
Depreciation and amortization									7,092	10,645	9,775
Income (Loss) from Operations									12,047	933	13,339
Capital Expenditures									2,308	5,217	4,216
Total Assets	100,351				115,537				100,351	115,537	146,480
Goodwill	40,839				41,500				40,839	41,500	41,500
Customer Technology Services | Operating Segments
Segment Reporting Information [Line Items]
Net Revenue									138,918	141,865	157,838
Customer Technology Services | Intersegment Eliminations
Segment Reporting Information [Line Items]
Net Revenue									(337)	(611)	(232)
Customer Strategy Services
Segment Reporting Information [Line Items]
Net Revenue									68,326	68,674	86,856
Depreciation and amortization									2,263	3,355	3,335
Income (Loss) from Operations									2,433	(5,691)	15,746
Capital Expenditures									710	1,109	1,128
Total Assets	67,755				73,548				67,755	73,548	96,086
Goodwill	$ 21,919				$ 21,120				21,919	21,120	25,026	$ 22,000
Customer Strategy Services | Operating Segments
Segment Reporting Information [Line Items]
Net Revenue									68,326	68,674	86,856
Customer Strategy Services | Intersegment Eliminations
Segment Reporting Information [Line Items]
Net Revenue									$ 0	$ 0	$ 0