Summary of Available-for-Sale Securities (Detail) - USD ($)	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 87,919,000	$ 102,529,000
Gross Unrealized Gain	106,000	677,000
Gross Unrealized Loss	(255,000)	(3,000)
Allowance for Credit Loss	0	0	$ 0
Fair Value	87,770,000	103,203,000
Money market funds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	7,170,000	6,203,000
Gross Unrealized Gain	0	0
Gross Unrealized Loss	0	0
Allowance for Credit Loss	0	0
Fair Value	7,170,000	6,203,000
United States government agency securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	25,761,000	29,570,000
Gross Unrealized Gain	1,000	66,000
Gross Unrealized Loss	(77,000)	0
Allowance for Credit Loss	0	0
Fair Value	25,685,000	29,636,000
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	52,611,000	66,756,000
Gross Unrealized Gain	105,000	611,000
Gross Unrealized Loss	(156,000)	(3,000)
Allowance for Credit Loss	0	0
Fair Value	52,560,000	$ 67,364,000
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,377,000
Gross Unrealized Gain	0
Gross Unrealized Loss	(22,000)
Allowance for Credit Loss	0
Fair Value	$ 2,355,000