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)

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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, 2019
Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost $ 209,985 $ 221,454
Fair Value 211,561 220,645
Short-term investments [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 150,517 137,532
Gross Unrealized Gains 240 7
Gross Unrealized Losses (5) (103)
Fair Value 150,752 137,436
Short-term investments [Member] | U.S. Treasuries [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 124,389 121,252
Gross Unrealized Gains 196 7
Gross Unrealized Losses (5) (79)
Fair Value 124,580 121,180
Short-term investments [Member] | U.S. Government Sponsored Entities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 0 3,512
Gross Unrealized Gains 0 0
Gross Unrealized Losses 0 (7)
Fair Value 0 3,505
Short-term investments [Member] | Corporate debt [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 26,128 11,962
Gross Unrealized Gains 44 0
Gross Unrealized Losses 0 (11)
Fair Value 26,172 11,951
Short-term investments [Member] | ABS and other [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 0 806
Gross Unrealized Gains 0 0
Gross Unrealized Losses 0 (6)
Fair Value 0 800
Long-term marketable securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 59,468 83,922
Gross Unrealized Gains 1,358 143
Gross Unrealized Losses (17) (856)
Fair Value 60,809 83,209
Long-term marketable securities [Member] | U.S. Treasuries [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 24,188 44,997
Gross Unrealized Gains 235 128
Gross Unrealized Losses 0 (115)
Fair Value 24,423 45,010
Long-term marketable securities [Member] | U.S. Government Sponsored Entities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 1,353 1,569
Gross Unrealized Gains 3 0
Gross Unrealized Losses (1) (62)
Fair Value 1,355 1,507
Long-term marketable securities [Member] | Corporate debt [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 25,447 32,467
Gross Unrealized Gains 1,027 3
Gross Unrealized Losses (3) (633)
Fair Value 26,471 31,837
Long-term marketable securities [Member] | ABS and other [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 8,480 4,889
Gross Unrealized Gains 93 12
Gross Unrealized Losses (13) (46)
Fair Value $ 8,560 $ 4,855