Available-for-Sale Debt Securities by Original Contractual Maturity (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Investments Debt And Equity Securities [Abstract]
One year or less, amortized cost	$ 54,471	$ 43,822
Greater than one year and less than five years, amortized cost	55,811	15,656
Amortized Cost	110,282	59,478
One year or less, fair value	54,565	43,907
Greater than one year and less than five years, fair value	55,594	15,685
Total available-for-sale securities fair value	$ 110,159	$ 59,592

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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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-Section 50
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in second through fifth fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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