Summary of Available-for-Sale Securities (Detail) - USD ($)	Sep. 30, 2022	Dec. 31, 2021	Sep. 30, 2021
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 83,375,000	$ 87,919,000
Gross Unrealized Gain	0	106,000
Gross Unrealized Loss	(3,188,000)	(255,000)
Allowance for Credit Loss	0	0	$ 0
Fair Value	80,187,000	87,770,000
Money market funds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,235,000	7,170,000
Gross Unrealized Gain	0	0
Gross Unrealized Loss	0	0
Allowance for Credit Loss	0	0
Fair Value	5,235,000	7,170,000
United States government agency securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	28,308,000	25,761,000
Gross Unrealized Gain	0	1,000
Gross Unrealized Loss	(895,000)	(77,000)
Allowance for Credit Loss	0	0
Fair Value	27,413,000	25,685,000
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	46,280,000	52,611,000
Gross Unrealized Gain	0	105,000
Gross Unrealized Loss	(1,935,000)	(156,000)
Allowance for Credit Loss	0	0
Fair Value	44,345,000	52,560,000
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,552,000	2,377,000
Gross Unrealized Gain	0	0
Gross Unrealized Loss	(358,000)	(22,000)
Allowance for Credit Loss	0	0
Fair Value	$ 3,194,000	$ 2,355,000