FAIR VALUE MEASUREMENTS - SCHEDULE OF SHORT-TERM INVESTMENTS (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Short-term investments, amortized cost	$ 28,881	$ 32,914
Short-term investments, gross unrealized holding gains	0	0
Short-term investments, gross unrealized holding losses	(21)	(7)
Short-term investments, fair value	28,860	32,907
U.S. Treasury securities
Schedule of Available-for-sale Securities [Line Items]
Short-term investments, amortized cost	28,881	32,914
Short-term investments, gross unrealized holding gains	0	0
Short-term investments, gross unrealized holding losses	(21)	(7)
Short-term investments, fair value	$ 28,860	$ 32,907