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)

v3.21.1
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, 2021
Dec. 31, 2020
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost $ 199,574 $ 203,329
Allowance for Credit Losses 0  
Fair Value 201,425 206,031
Short-term investments [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 134,460 158,148
Allowance for Credit Losses 0 0
Gross Unrealized Gains 34 116
Gross Unrealized Losses 0 (6)
Fair Value 134,494 158,258
Short-term investments [Member] | U.S. Treasuries [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 69,217 75,887
Allowance for Credit Losses 0 0
Gross Unrealized Gains 23 88
Gross Unrealized Losses 0 (5)
Fair Value 69,240 75,970
Short-term investments [Member] | U.S. Government Sponsored Entities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 11,450 32,439
Allowance for Credit Losses 0 0
Gross Unrealized Gains 4 8
Gross Unrealized Losses 0 0
Fair Value 11,454 32,447
Short-term investments [Member] | Corporate debt [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 53,793 49,822
Allowance for Credit Losses 0 0
Gross Unrealized Gains 7 20
Gross Unrealized Losses 0 (1)
Fair Value 53,800 49,841
Long-term marketable securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 65,114 45,181
Allowance for Credit Losses 0 0
Gross Unrealized Gains 1,886 2,636
Gross Unrealized Losses (69) (44)
Fair Value 66,931 47,773
Long-term marketable securities [Member] | U.S. Treasuries [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 22,342 3,375
Allowance for Credit Losses 0 0
Gross Unrealized Gains 179 266
Gross Unrealized Losses 0 0
Fair Value 22,521 3,641
Long-term marketable securities [Member] | U.S. Government Sponsored Entities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 1,012 1,114
Allowance for Credit Losses 0 0
Gross Unrealized Gains 36 38
Gross Unrealized Losses (3) 0
Fair Value 1,045 1,152
Long-term marketable securities [Member] | Corporate debt [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 35,424 34,183
Allowance for Credit Losses 0 0
Gross Unrealized Gains 1,505 2,137
Gross Unrealized Losses (60) (33)
Fair Value 36,869 36,287
Long-term marketable securities [Member] | Asset-backed Securities ("ABS") and Other [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 6,336 6,509
Allowance for Credit Losses 0 0
Gross Unrealized Gains 166 195
Gross Unrealized Losses (6) (11)
Fair Value $ 6,496 $ 6,693