QUARTERLY RESULTS OF OPERATIONS (UNAUDITED) (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 11,464	$ 10,624	$ 8,743	$ 5,122	$ 10,867	$ 8,552	$ 6,144	$ 85,416	$ 35,953	$ 110,979	$ 35,013
Gross profit	11,411	10,562	8,703	5,107	10,839	8,491	6,050	85,381	35,783	110,761
Operating income (loss)	478	(1,275)	(9,155)	(11,499)	(3,546)	(5,163)	(8,295)	70,105	(21,451)	53,101	(45,422)
Income (loss) before provision for taxes	1,250	(1,299)	(8,623)	(10,901)	(3,063)	(4,618)	(7,920)	70,336	(19,573)	54,735	(44,811)
Benefit (provision) for income taxes	(271)	(88)	3	(115)	(79)	(22)	162	(453)	(471)	(392)	(480)
Net income (loss)	$ 979	$ (1,387)	$ (8,620)	$ (11,016)	$ (3,142)	$ (4,640)	$ (7,758)	$ 69,883	$ (20,044)	$ 54,343	$ (45,291)
Basic net income (loss) per share (in dollars per share)	$ 0.03	$ (0.04)	$ (0.27)	$ (0.35)	$ (0.10)	$ (0.15)	$ (0.25)	$ 2.35	$ (0.64)	$ 1.78	$ (1.55)
Shares used in calculating basic net income (loss) per share (in shares)	31,731	31,711	31,578	31,089	30,814	30,780	30,527	29,700	31,529	30,459	29,179
Diluted net income (loss) per share (in dollars per shares)	$ 0.03	$ (0.04)	$ (0.27)	$ (0.35)	$ (0.10)	$ (0.15)	$ (0.25)	$ 2.29	$ (0.64)	$ 1.73	$ (1.55)
Shares used in calculating diluted net income (loss) per share (in shares)	31,904	31,711	31,578	31,089	30,814	30,780	30,527	30,566	31,529	31,407	29,179