Financial Instruments - Fair Value Measured On A Recurring Basis (Detail) - USD ($)	Jun. 30, 2023	Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	$ 55,805,000	$ 57,534,000
Long-term investments	26,023,000	41,978,000
Assets measured at fair value	274,377,000	328,641,000
Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets measured at fair value	206,278,000	249,139,000
Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets measured at fair value	68,099,000	79,502,000
U.S. government agency bonds | Fair Value, Measurements, Recurring | Short-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	4,133,000
U.S. government agency bonds | Fair Value, Measurements, Recurring | Level 1 | Short-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	0
U.S. government agency bonds | Fair Value, Measurements, Recurring | Level 2 | Short-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	4,133,000
U.S. government treasury bonds | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	9,096,000	15,404,000
Long-term investments	4,633,000	4,606,000
U.S. government treasury bonds | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	9,096,000	15,404,000
Long-term investments	4,633,000	4,606,000
U.S. government treasury bonds | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	0	0
Long-term investments	0	0
Corporate bonds | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	39,145,000	36,510,000
Long-term investments	18,818,000	29,965,000
Corporate bonds | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	0	0
Long-term investments	0	0
Corporate bonds | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	39,145,000	36,510,000
Long-term investments	18,818,000	29,965,000
Municipal bonds | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	1,419,000	2,711,000
Long-term investments		675,000
Municipal bonds | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	0	0
Long-term investments		0
Municipal bonds | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	1,419,000	2,711,000
Long-term investments		675,000
U.S. government agency bonds | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Long-term investments	997,000	5,163,000
U.S. government agency bonds | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Long-term investments	0	0
U.S. government agency bonds | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Long-term investments	997,000	5,163,000
Asset-backed securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	2,012,000	2,909,000
Long-term investments	1,575,000	1,569,000
Asset-backed securities | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	0	0
Long-term investments	0	0
Asset-backed securities | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	2,012,000	2,909,000
Long-term investments	1,575,000	1,569,000
Money market funds | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	192,549,000	229,129,000
Money market funds | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	192,549,000	229,129,000
Money market funds | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	$ 0	$ 0