Available-for-Sale Marketable Securities - Schedule of Amortized Cost and Fair Values of Marketable Debt Securities by Contractual Maturity (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Investments Debt And Equity Securities [Abstract]
Amortized Cost of marketable debt securities, contractual maturity, less than one year	$ 149,164	$ 136,565
Amortized Cost of marketable debt securities, contractual maturity, One year to three years	70,570	63,125
Amortized Cost	219,734	199,690
Fair value of marketable debt securities, contractual maturities, less than one year	149,242	136,701
Fair value of marketable debt securities, contractual maturity, One year to three years	70,565	63,159
Total fair Value of marketable debt securities, contractual maturity	219,807	199,860
Proceeds from sale of available-for-sale marketable securities	41,600	0	$ 79,808
Realized gain (loss)	272		$ (5)
Interest receivable	$ 311	$ 971

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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Amount 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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Amount of realized gain (loss) on 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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Carrying amount as of the balance sheet date of current interest earned but not received. Also called accrued interest or accrued interest receivable. For classified balance sheets, represents the current amount receivable, that is amounts expected to be collected within one year or the normal operating cycle, if longer.

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Amount of cash inflow from sale 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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