The Company and Significant Accounting Policies - Summary of Amortized Cost and Unrealized (Gains) Losses of Available for Sale Securities (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($)
Certificates of Deposit
Amortized Cost
Due within a year	$ 3,360
Due after one year through five years	4,202
Total	7,562
Unrealized gains (losses)
Due within a year	(3)
Due after one year through five years	1
Total	(2)
Corporate Bonds
Amortized Cost
Due within a year	35,056
Due after one year through five years	80,268
Total	115,324
Unrealized gains (losses)
Due within a year	(48)
Due after one year through five years	(266)
Total	$ (314)