INCOME TAXES - Details of Significant Components of Net Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Net operating loss carryforwards	$ 4,968	$ 13,394
State income taxes	1	1
Deferred revenue	2,347	5,349
Research and development and other credits	9,590	11,447
Reserves and accruals recognized in different periods	3,734	3,088
Basis difference in investment	0	583
Capitalized R&D expenses	3,415	3,623
Depreciation and amortization	472	413
Deferred rent	160	183
Other	6	0
Total deferred tax assets	24,693	38,081
Valuation allowance	(24,398)	(37,680)
Net deferred tax assets	295	401
Foreign credits	(29)	(43)
Other	(17)	0
Net deferred tax liabilities	(46)	(43)
Net deferred taxes	$ 249	$ 358