INCOME TAXES - DEFERRED TAX ASSETS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Net operating losses	$ 16,391	$ 6,810
Tax credit carryforwards	1,860	1,452
Intangibles	38,509	46,364
Stock-based compensation	1,505	4,992
Reserves and other accruals not currently deductible	12,094	17,294
Total deferred tax assets	70,359	76,912
Valuation allowance for deferred tax assets	(54,224)	(45,206)
Deferred tax assets	16,135	31,706
Deferred tax liabilities
Convertible debt	(16,135)	(31,706)
Increase (decrease) in valuation allowance	9,000	44,600	$ (3,700)
Activity related to unrecognized tax benefits
Accrued interest and penalties associated with unrecognized tax benefits	800
Unrecognized tax benefits at the beginning of the period	14,687	5,686	5,179
Gross increases - current year tax positions	3,423	240	454
Gross increases - prior year tax positions		8,761	53
Gross increases - prior year tax positions	(966)
Unrecognized tax benefits at the end of the period	17,144	14,687	$ 5,686
Unrecognized tax benefit that would affect the effective tax rate	$ 10,800	$ 12,200