Amortized Cost and Fair Value of Available-for-Sale Investments (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 161,911	$ 169,293
Gross Unrealized Gains	0	1
Gross Unrealized Losses	9,542	10,764
Fair Value	152,369	158,530
Money market investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	16,032	21,910
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	16,032	21,910
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	17,044	18,905
Gross Unrealized Gains	0	0
Gross Unrealized Losses	2,708	2,889
Fair Value	14,336	16,016
Corporate bonds and direct obligations of government agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	119,632	126,134
Gross Unrealized Gains	0	1
Gross Unrealized Losses	6,758	7,775
Fair Value	112,874	118,360
U.S. Treasury obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	9,203	2,344
Gross Unrealized Gains	0	0
Gross Unrealized Losses	76	100
Fair Value	$ 9,127	$ 2,244