INCOME TAXES - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Allowances and reserves	$ 10,726	$ 10,022
Net operating loss and tax credit carryforwards	54,369	71,568
Stock-based compensation	3,753	3,662
Deferred revenue	16,736	19,562
Fixed assets and intangibles	2,720	3,836
Sec. 163(j) interest carryforward	0	2,064
Other	1,109	2,084
Subtotal	89,413	112,798
Less valuation allowance	0	(98,631)
Total deferred tax assets, net of valuation allowance	89,413	14,167
Deferred tax liabilities:
Goodwill	(1,368)	(1,070)
Unremitted foreign earnings	(5)	(16)
Deferred cost of goods sold	(14,374)	(12,655)
Total deferred tax liabilities	(15,747)	(13,741)
Net deferred tax asset	$ 73,666	$ 426