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Short-Term and Long-Term Investments - Summary of Investment (Detail) - USD ($)
$ in Thousands
Dec. 31, 2020
Dec. 31, 2019
Cash and Cash Equivalents [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Debt Securities, Available-for-sale $ 161,742 $ 84,668
Short-term Investments [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Debt Securities, Available-for-sale 50,166  
Other Long-term Investments [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Debt Securities, Available-for-sale 2,517 2,510
Estimate of Fair Value Measurement [Member] | Cash and Cash Equivalents [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Debt Securities, Available-for-sale 89,491 9,630
Estimate of Fair Value Measurement [Member] | Short-term Investments [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Debt Securities, Available-for-sale 50,166  
Estimate of Fair Value Measurement [Member] | Other Long-term Investments [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Debt Securities, Available-for-sale 2,517 2,510
Estimate of Fair Value Measurement [Member] | Auction Rate Securities [Member] | Other Long-term Investments [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Debt Securities, Available-for-sale 2,517 2,510
Estimate of Fair Value Measurement [Member] | Money Market Funds [Member] | Cash and Cash Equivalents [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Debt Securities, Available-for-sale 69,493 9,630
Estimate of Fair Value Measurement [Member] | US Treasury Obligations [Member] | Cash and Cash Equivalents [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Debt Securities, Available-for-sale 19,998  
Estimate of Fair Value Measurement [Member] | US Treasury Obligations [Member] | Short-term Investments [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Debt Securities, Available-for-sale 50,166  
Portion at Other than Fair Value Measurement [Member] | Cash [Member] | Cash and Cash Equivalents [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Debt Securities, Available-for-sale $ 72,251 $ 75,038