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)

v3.20.1
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
Mar. 31, 2020
Dec. 31, 2019
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost $ 188,069 $ 209,985
Allowance for Credit Losses 0  
Fair Value 189,074 211,561
Short-term investments [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 143,115 150,517
Allowance for Credit Losses 0  
Gross Unrealized Gains 849 240
Gross Unrealized Losses (100) (5)
Fair Value 143,864 150,752
Short-term investments [Member] | U.S. Treasuries [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 113,885 124,389
Allowance for Credit Losses 0  
Gross Unrealized Gains 835 196
Gross Unrealized Losses 0 (5)
Fair Value 114,720 124,580
Short-term investments [Member] | U.S. Government Sponsored Entities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 9,128 0
Allowance for Credit Losses 0  
Gross Unrealized Gains 9 0
Gross Unrealized Losses 0 0
Fair Value 9,137 0
Short-term investments [Member] | Corporate debt [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 19,801 26,128
Allowance for Credit Losses 0  
Gross Unrealized Gains 5 44
Gross Unrealized Losses (95) 0
Fair Value 19,711 26,172
Short-term investments [Member] | ABS and other [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 301  
Allowance for Credit Losses 0  
Gross Unrealized Gains 0  
Gross Unrealized Losses (5)  
Fair Value 296  
Long-term marketable securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 44,954 59,468
Allowance for Credit Losses 0  
Gross Unrealized Gains 1,202 1,358
Gross Unrealized Losses (946) (17)
Fair Value 45,210 60,809
Long-term marketable securities [Member] | U.S. Treasuries [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 10,015 24,188
Allowance for Credit Losses 0  
Gross Unrealized Gains 495 235
Gross Unrealized Losses 0 0
Fair Value 10,510 24,423
Long-term marketable securities [Member] | U.S. Government Sponsored Entities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 1,299 1,353
Allowance for Credit Losses 0  
Gross Unrealized Gains 29 3
Gross Unrealized Losses 0 (1)
Fair Value 1,328 1,355
Long-term marketable securities [Member] | Corporate debt [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 25,633 25,447
Allowance for Credit Losses 0  
Gross Unrealized Gains 634 1,027
Gross Unrealized Losses (661) (3)
Fair Value 25,606 26,471
Long-term marketable securities [Member] | ABS and other [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 8,007 8,480
Allowance for Credit Losses 0  
Gross Unrealized Gains 44 93
Gross Unrealized Losses (285) (13)
Fair Value $ 7,766 $ 8,560