MERGER - Additional Information (Detail) - USD ($)	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	Feb. 10, 2017
Business Acquisition [Line Items]
Goodwill												$ 77,592,000
Goodwill deductible for income tax purposes												$ 0
Goodwill impairment									$ 0	$ 0	$ 77,592,000
Net loss	$ (37,541,000)	$ (39,607,000)	$ (40,493,000)	$ (34,126,000)	$ (31,516,000)	$ (33,191,000)	$ (35,854,000)	$ (25,184,000)	$ (151,767,000)	$ (125,745,000)	(231,459,000)
Parallax Services
Business Acquisition [Line Items]
Net loss											$ 800,000