Fair Value of Financial Instruments - Summary of Contractual Maturities of Short and Long Term Investments (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Amortized Cost Basis, Due within one year	$ 782,054	$ 872,637
Amortized Cost Basis, Due after 1 year through 2 years	106,080	30,640
Amortized Cost	888,134	903,277
Aggregate Fair Value, Due within one year	782,335	873,073
Aggregate Fair Value, Due after 1 year through 2 years	105,990	30,697
Aggregate Fair Value, Total	$ 888,325	$ 903,770

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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