Fair Value Measurements - Fair Values and Unrealized Losses on Corporate Debt Investments (Detail) - Corporate Debt [Member] - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Schedule Of Available For Sale Securities [Line Items]
Less than Twelve Months, Fair value	$ 1,369	$ 27,999
Less than Twelve Months, Gross unrealized losses		(18)
Twelve Months or More, Fair value		4,406
Twelve Months or More, Gross unrealized losses		(1)
Fair value, Total		32,405
Gross unrealized losses, Total		$ (19)

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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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), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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