SEGMENT REPORTING (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) operating_segments	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Segment Reporting Information [Line Items]
Number of business segments (in segments) | operating_segments	2
Segment Reporting Information, Revenue [Abstract]
Revenues	$ 837,630	$ 711,764	$ 575,936
Reconciliation of EBITDA to net income [Abstract]
Net income (loss)	85,071	(3,465)	44,869
Amortization of acquired intangible assets in cost of revenues	22,819	30,077	26,290
Amortization of acquired intangible assets in operating expenses	22,731	27,931	28,432
Depreciation and other amortization	24,615	20,524	15,650
Interest and other income	(1,773)	(537)	(516)
Interest and other expense	10,016	9,411	10,481
Income tax expense, net	51,591	6,046	26,044
EBITDA	215,070	89,987	151,250
International [Member]
Segment Reporting Information, Revenue [Abstract]
Revenues	28,178	25,232	23,852
Operating Segments [Member] | North America [Member]
Segment Reporting Information [Line Items]
North America corporate allocation	396	954	1,000
Segment Reporting Information, Revenue [Abstract]
Revenues	809,492	686,573	552,141
Reconciliation of EBITDA to net income [Abstract]
EBITDA	210,901	87,092	148,913
Operating Segments [Member] | International [Member]
Segment Reporting Information [Line Items]
International corporate allocation	321	256	261
Reconciliation of EBITDA to net income [Abstract]
EBITDA	4,169	2,895	2,337
Operating Segments [Member] | International [Member] | External Customers [Member]
Segment Reporting Information, Revenue [Abstract]
Revenues	28,138	25,191	23,795
Intersegment Revenue [Member]
Segment Reporting Information, Revenue [Abstract]
Revenues	40	41	57
Intersegment Eliminations [Member]
Segment Reporting Information, Revenue [Abstract]
Revenues	$ (40)	$ (41)	$ (57)