QUARTERLY RESULTS OF OPERATIONS (UNAUDITED) - Quarterly Consolidated Statement of Operations Data (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 10,867	$ 8,552	$ 6,144	$ 85,416	$ 6,896	$ 11,863	$ 7,030	$ 9,224
Gross profit	10,839	8,491	6,050	85,381	6,857	11,802	6,976	9,181
Operating income (loss)	(3,546)	(5,163)	(8,295)	70,105	(12,216)	(5,443)	(14,911)	(12,852)	$ 53,101	$ (45,422)	$ (15,263)
Income (loss) from continuing operations before provisions for income taxes	(3,063)	(4,618)	(7,920)	70,336	(12,109)	(5,243)	(14,746)	(12,713)	54,735	(44,811)	(14,509)
Benefit (provision) for income taxes	(79)	(22)	162	(453)	(185)	(44)	(99)	(152)	(392)	(480)	(25,521)
Net income (loss)	$ (3,142)	$ (4,640)	$ (7,758)	$ 69,883	$ (12,294)	$ (5,287)	$ (14,845)	$ (12,865)	$ 54,343	$ (45,291)	$ (39,381)
Basic net income (loss) per share (in dollars per share)	$ (0.10)	$ (0.15)	$ (0.25)	$ 2.35	$ (0.42)	$ (0.18)	$ (0.51)	$ (0.44)	$ 1.78	$ (1.55)	$ (1.37)
Shares used in calculating basic net income (loss) per share (in shares)	30,814	30,780	30,527	29,700	29,250	29,245	29,193	29,024	30,459	29,179	28,759
Diluted net income (loss) per share (in dollars per shares)	$ (0.10)	$ (0.15)	$ (0.25)	$ 2.29	$ (0.42)	$ (0.18)	$ (0.51)	$ (0.44)	$ 1.73	$ (1.55)	$ (1.37)
Shares used in calculating diluted net income (loss) per share (in shares)	30,814	30,780	30,527	30,566	29,250	29,245	29,193	29,024	31,407	29,179	28,759