Annual report pursuant to Section 13 and 15(d)

Investments in Marketable Securities - Schedule of Amortized Cost and Fair Value of Marketable Securities, Available-for-Sale, by Type of Security (Detail)

v3.20.4
Investments in Marketable Securities - Schedule of Amortized Cost and Fair Value of Marketable Securities, Available-for-Sale, by Type of Security (Detail) - USD ($)
$ in Thousands
Dec. 31, 2020
Dec. 31, 2019
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost $ 203,329 $ 209,985
Allowance for Credit Losses 0  
Fair Value 206,031 211,561
Short-term investments [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 158,148 150,517
Allowance for Credit Losses 0  
Gross Unrealized Gains 116 240
Gross Unrealized Losses (6) (5)
Fair Value 158,258 150,752
Short-term investments [Member] | U.S. Treasuries [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 75,887 124,389
Allowance for Credit Losses 0  
Gross Unrealized Gains 88 196
Gross Unrealized Losses (5) (5)
Fair Value 75,970 124,580
Short-term investments [Member] | U.S. Government Sponsored Entities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 32,439  
Allowance for Credit Losses 0  
Gross Unrealized Gains 8  
Gross Unrealized Losses 0  
Fair Value 32,447  
Short-term investments [Member] | Corporate debt [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 49,822 26,128
Allowance for Credit Losses 0  
Gross Unrealized Gains 20 44
Gross Unrealized Losses (1) 0
Fair Value 49,841 26,172
Long-term marketable securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 45,181 59,468
Allowance for Credit Losses 0  
Gross Unrealized Gains 2,636 1,358
Gross Unrealized Losses (44) (17)
Fair Value 47,773 60,809
Long-term marketable securities [Member] | U.S. Treasuries [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 3,375 24,188
Allowance for Credit Losses 0  
Gross Unrealized Gains 266 235
Gross Unrealized Losses 0 0
Fair Value 3,641 24,423
Long-term marketable securities [Member] | U.S. Government Sponsored Entities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 1,114 1,353
Allowance for Credit Losses 0  
Gross Unrealized Gains 38 3
Gross Unrealized Losses 0 (1)
Fair Value 1,152 1,355
Long-term marketable securities [Member] | Corporate debt [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 34,183 25,447
Allowance for Credit Losses 0  
Gross Unrealized Gains 2,137 1,027
Gross Unrealized Losses (33) (3)
Fair Value 36,287 26,471
Long-term marketable securities [Member] | ABS and other [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 6,509 8,480
Allowance for Credit Losses 0  
Gross Unrealized Gains 195 93
Gross Unrealized Losses (11) (13)
Fair Value $ 6,693 $ 8,560