INCOME TAXES (Components of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Reserve for bad debts	$ 1,457	$ 1,636
Accrued compensation	4,803	6,706
Stock compensation	10,041	10,568
Net operating losses	26,349	25,899
Accrued reserve and other	1,773	1,578
Deferred rent	5,928	6,533
Deferred gain on the sale of building	4,140	4,741
Research and development credits	6,331	0
Total deferred tax assets, prior to valuation allowance	60,822	57,661
Valuation allowance	(14,246)	(13,032)
Total deferred tax assets, net of valuation allowance	46,576	44,629
Deferred tax liabilities:
Deferred commission costs, net	(19,314)	0
Prepaid expenses	(2,204)	(1,239)
Property and equipment, net	(5,367)	(6,229)
Intangible assets, net	(82,079)	(43,800)
Total deferred tax liabilities	(108,964)	(51,268)
Net deferred tax assets (liabilities)	$ (62,388)	$ (6,639)