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Cash, Cash Equivalents and Investments - Amortized Cost to Fair Value (Detail) $ in Thousands | Dec. 31, 2020 USD ($)
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Debt Securities, Available-for-sale [Line Items] |
Amortized Cost | $ 492,675
Gross Unrealized Gains | 5,690
Fair Value, Total | 498,365
Treasury Bills [Member] |
Debt Securities, Available-for-sale [Line Items] |
Fair Value, Total | 131,861
Treasury Bills [Member] | Short-term Investments [Member] |
Debt Securities, Available-for-sale [Line Items] |
Amortized Cost | 34,978
Gross Unrealized Gains | 425
Gross Unrealized Losses | 0
Fair Value, Total | 35,403
Treasury Bills [Member] | Long-term investments [Member] |
Debt Securities, Available-for-sale [Line Items] |
Amortized Cost | 95,522
Gross Unrealized Gains | 936
Gross Unrealized Losses | 0
Fair Value, Total | 96,458
Asset-Backed Securities [Member] |
Debt Securities, Available-for-sale [Line Items] |
Fair Value, Total | 92,218
Asset-Backed Securities [Member] | Short-term Investments [Member] |
Debt Securities, Available-for-sale [Line Items] |
Amortized Cost | 24,999
Gross Unrealized Gains | 161
Gross Unrealized Losses | 0
Fair Value, Total | 25,160
Asset-Backed Securities [Member] | Long-term investments [Member] |
Debt Securities, Available-for-sale [Line Items] |
Amortized Cost | 66,329
Gross Unrealized Gains | 729
Gross Unrealized Losses | 0
Fair Value, Total | 67,058
Corporate Bonds [Member] |
Debt Securities, Available-for-sale [Line Items] |
Fair Value, Total | 236,142
Corporate Bonds [Member] | Short-term Investments [Member] |
Debt Securities, Available-for-sale [Line Items] |
Amortized Cost | 32,394
Gross Unrealized Gains | 320
Gross Unrealized Losses | 0
Fair Value, Total | 32,714
Corporate Bonds [Member] | Long-term investments [Member] |
Debt Securities, Available-for-sale [Line Items] |
Amortized Cost | 200,549
Gross Unrealized Gains | 2,879
Gross Unrealized Losses | 0
Fair Value, Total | 203,428
Sovereign Bonds [Member] |
Debt Securities, Available-for-sale [Line Items] |
Fair Value, Total | 12,100
Sovereign Bonds [Member] | Short-term Investments [Member] |
Debt Securities, Available-for-sale [Line Items] |
Amortized Cost | 8,590
Gross Unrealized Gains | 70
Gross Unrealized Losses | 0
Fair Value, Total | 8,660
Sovereign Bonds [Member] | Long-term investments [Member] |
Debt Securities, Available-for-sale [Line Items] |
Amortized Cost | 3,379
Gross Unrealized Gains | 61
Gross Unrealized Losses | 0
Fair Value, Total | 3,440
Municipal Bonds [Member] |
Debt Securities, Available-for-sale [Line Items] |
Fair Value, Total | 7,038
Municipal Bonds [Member] | Short-term Investments [Member] |
Debt Securities, Available-for-sale [Line Items] |
Amortized Cost | 1,297
Gross Unrealized Gains | 6
Gross Unrealized Losses | 0
Fair Value, Total | 1,303
Municipal Bonds [Member] | Long-term investments [Member] |
Debt Securities, Available-for-sale [Line Items] |
Amortized Cost | 5,725
Gross Unrealized Gains | 10
Gross Unrealized Losses |
Fair Value, Total | 5,735
Agency Bonds [Member] |
Debt Securities, Available-for-sale [Line Items] |
Fair Value, Total | 19,006
Agency Bonds [Member] | Long-term investments [Member] |
Debt Securities, Available-for-sale [Line Items] |
Amortized Cost | 18,913
Gross Unrealized Gains | 93
Gross Unrealized Losses | 0
Fair Value, Total | $ 19,006

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