Summary of Income Tax Current and Deferred Provision (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current:
State	$ 22	$ 30	$ 27
Foreign	69	87	25
Total current income tax provision	91	117	52
Deferred:
Federal	60	61	60
Total deferred income tax provision	60	61	60
Total income tax provision	$ 151	$ 178	$ 112