Quarterly report pursuant to Section 13 or 15(d)

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

v3.20.2
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
Jun. 30, 2020
Dec. 31, 2019
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost $ 210,003 $ 209,985
Allowance for Credit Losses 0  
Fair Value 212,549 211,561
Short-term investments [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 169,195 150,517
Allowance for Credit Losses 0  
Gross Unrealized Gains 574 240
Gross Unrealized Losses (1) (5)
Fair Value 169,768 150,752
Short-term investments [Member] | U.S. Treasuries [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 108,982 124,389
Allowance for Credit Losses 0  
Gross Unrealized Gains 498 196
Gross Unrealized Losses (1) (5)
Fair Value 109,479 124,580
Short-term investments [Member] | U.S. Government Sponsored Entities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 37,699 0
Allowance for Credit Losses 0  
Gross Unrealized Gains 14 0
Gross Unrealized Losses 0 0
Fair Value 37,713 0
Short-term investments [Member] | Corporate debt [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 22,514 26,128
Allowance for Credit Losses 0  
Gross Unrealized Gains 62 44
Gross Unrealized Losses 0 0
Fair Value 22,576 26,172
Long-term marketable securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 40,808 59,468
Allowance for Credit Losses 0  
Gross Unrealized Gains 2,241 1,358
Gross Unrealized Losses (268) (17)
Fair Value 42,781 60,809
Long-term marketable securities [Member] | U.S. Treasuries [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 3,892 24,188
Allowance for Credit Losses 0  
Gross Unrealized Gains 319 235
Gross Unrealized Losses 0 0
Fair Value 4,211 24,423
Long-term marketable securities [Member] | U.S. Government Sponsored Entities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 1,218 1,353
Allowance for Credit Losses 0  
Gross Unrealized Gains 36 3
Gross Unrealized Losses 0 (1)
Fair Value 1,254 1,355
Long-term marketable securities [Member] | Corporate debt [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 28,139 25,447
Allowance for Credit Losses 0  
Gross Unrealized Gains 1,758 1,027
Gross Unrealized Losses (181) (3)
Fair Value 29,716 26,471
Long-term marketable securities [Member] | ABS and other [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 7,559 8,480
Allowance for Credit Losses 0  
Gross Unrealized Gains 128 93
Gross Unrealized Losses (87) (13)
Fair Value $ 7,600 $ 8,560