Accumulated Other Comprehensive Income (Loss) - Summary of Changes in Accumulated Other Comprehensive Income (Loss), Net of Tax, from Unrealized Gains (Losses) on Available-for-Sale Marketable Securities (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Total Accumulated Other Comprehensive Income (Loss), Beginning Balance	$ 3	$ (35)
Other comprehensive income before reclassifications	(13)	76
Amount reclassified from accumulated other comprehensive income	(3)
Net current period other comprehensive income	(16)	76
Total Accumulated Other Comprehensive Income (Loss), Ending Balance	$ (13)	$ 41