Financial Instruments - Fair Value Measured On A Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, short-term	$ 71,972	$ 0
Marketable securities, long-term	125,320	0
Assets measured at fair value	554,322	528,136
Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets measured at fair value	385,938	519,228
Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets measured at fair value	159,763	3,500
Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets measured at fair value	8,621	5,408
Money market funds | Fair Value, Measurements, Recurring | Cash equivalents:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	343,010	519,228
Money market funds | Fair Value, Measurements, Recurring | Level 1 | Cash equivalents:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	343,010	519,228
Money market funds | Fair Value, Measurements, Recurring | Level 2 | Cash equivalents:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	0	0
Money market funds | Fair Value, Measurements, Recurring | Level 3 | Cash equivalents:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	0	0
Corporate bonds | Fair Value, Measurements, Recurring | Cash equivalents:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	1,042
Corporate bonds | Fair Value, Measurements, Recurring | Short-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, short-term	35,065
Corporate bonds | Fair Value, Measurements, Recurring | Long-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, long-term	79,011
Corporate bonds | Fair Value, Measurements, Recurring | Level 1 | Cash equivalents:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	0
Corporate bonds | Fair Value, Measurements, Recurring | Level 1 | Short-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, short-term	0
Corporate bonds | Fair Value, Measurements, Recurring | Level 1 | Long-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, long-term	0
Corporate bonds | Fair Value, Measurements, Recurring | Level 2 | Cash equivalents:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	1,042
Corporate bonds | Fair Value, Measurements, Recurring | Level 2 | Short-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, short-term	35,065
Corporate bonds | Fair Value, Measurements, Recurring | Level 2 | Long-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, long-term	79,011
Corporate bonds | Fair Value, Measurements, Recurring | Level 3 | Cash equivalents:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	0
Corporate bonds | Fair Value, Measurements, Recurring | Level 3 | Short-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, short-term	0
Corporate bonds | Fair Value, Measurements, Recurring | Level 3 | Long-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, long-term	0
Municipal bonds | Fair Value, Measurements, Recurring | Cash equivalents:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	516
Municipal bonds | Fair Value, Measurements, Recurring | Short-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, short-term	3,657
Municipal bonds | Fair Value, Measurements, Recurring | Long-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, long-term	3,440
Municipal bonds | Fair Value, Measurements, Recurring | Level 1 | Cash equivalents:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	0
Municipal bonds | Fair Value, Measurements, Recurring | Level 1 | Short-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, short-term	0
Municipal bonds | Fair Value, Measurements, Recurring | Level 1 | Long-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, long-term	0
Municipal bonds | Fair Value, Measurements, Recurring | Level 2 | Cash equivalents:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	516
Municipal bonds | Fair Value, Measurements, Recurring | Level 2 | Short-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, short-term	3,657
Municipal bonds | Fair Value, Measurements, Recurring | Level 2 | Long-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, long-term	3,440
Municipal bonds | Fair Value, Measurements, Recurring | Level 3 | Cash equivalents:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	0
Municipal bonds | Fair Value, Measurements, Recurring | Level 3 | Short-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, short-term	0
Municipal bonds | Fair Value, Measurements, Recurring | Level 3 | Long-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, long-term	0
U.S. government treasury bonds | Fair Value, Measurements, Recurring | Short-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, short-term	22,251
U.S. government treasury bonds | Fair Value, Measurements, Recurring | Long-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, long-term	20,677
U.S. government treasury bonds | Fair Value, Measurements, Recurring | Level 1 | Short-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, short-term	22,251
U.S. government treasury bonds | Fair Value, Measurements, Recurring | Level 1 | Long-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, long-term	20,677
U.S. government treasury bonds | Fair Value, Measurements, Recurring | Level 2 | Short-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, short-term	0
U.S. government treasury bonds | Fair Value, Measurements, Recurring | Level 2 | Long-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, long-term	0
U.S. government treasury bonds | Fair Value, Measurements, Recurring | Level 3 | Short-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, short-term	0
U.S. government treasury bonds | Fair Value, Measurements, Recurring | Level 3 | Long-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, long-term	0
Asset-backed securities | Fair Value, Measurements, Recurring | Short-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, short-term	10,999
Asset-backed securities | Fair Value, Measurements, Recurring | Long-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, long-term	20,992
Asset-backed securities | Fair Value, Measurements, Recurring | Level 1 | Short-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, short-term	0
Asset-backed securities | Fair Value, Measurements, Recurring | Level 1 | Long-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, long-term	0
Asset-backed securities | Fair Value, Measurements, Recurring | Level 2 | Short-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, short-term	10,999
Asset-backed securities | Fair Value, Measurements, Recurring | Level 2 | Long-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, long-term	20,992
Asset-backed securities | Fair Value, Measurements, Recurring | Level 3 | Short-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, short-term	0
Asset-backed securities | Fair Value, Measurements, Recurring | Level 3 | Long-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, long-term	0
U.S. government agency bonds | Fair Value, Measurements, Recurring | Long-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, long-term	1,200
U.S. government agency bonds | Fair Value, Measurements, Recurring | Level 1 | Long-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, long-term	0
U.S. government agency bonds | Fair Value, Measurements, Recurring | Level 2 | Long-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, long-term	1,200
U.S. government agency bonds | Fair Value, Measurements, Recurring | Level 3 | Long-term investments:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities, long-term	0
Israeli funds | Fair Value, Measurements, Recurring | Prepaid expenses and other current assets:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Israeli funds	3,841	3,500
Israeli funds | Fair Value, Measurements, Recurring | Level 1 | Prepaid expenses and other current assets:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Israeli funds	0	0
Israeli funds | Fair Value, Measurements, Recurring | Level 2 | Prepaid expenses and other current assets:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Israeli funds	3,841	3,500
Israeli funds | Fair Value, Measurements, Recurring | Level 3 | Prepaid expenses and other current assets:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Israeli funds	0	0
Investments in privately held companies | Fair Value, Nonrecurring | Other assets:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments in privately held companies	8,621
Investments in privately held companies | Fair Value, Nonrecurring | Level 1 | Other assets:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments in privately held companies	0
Investments in privately held companies | Fair Value, Nonrecurring | Level 2 | Other assets:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments in privately held companies	0
Investments in privately held companies | Fair Value, Nonrecurring | Level 3 | Other assets:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments in privately held companies	$ 8,621
Current unsecured promissory note | Fair Value, Nonrecurring | Prepaid expenses and other current assets:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Current unsecured promissory note		5,408
Current unsecured promissory note | Fair Value, Nonrecurring | Level 1 | Prepaid expenses and other current assets:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Current unsecured promissory note		0
Current unsecured promissory note | Fair Value, Nonrecurring | Level 2 | Prepaid expenses and other current assets:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Current unsecured promissory note		0
Current unsecured promissory note | Fair Value, Nonrecurring | Level 3 | Prepaid expenses and other current assets:
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Current unsecured promissory note		$ 5,408