Other Long-Term Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Other Liabilities Disclosure [Abstract]
Deferred rent	$ 1,223	$ 1,850
Uncertain tax positions, interest and penalties not recognized	1,669	1,582
Accrued general and administrative expenses	3	4
Total other long-term liabilities	$ 2,895	$ 3,436