Available-for-Sale Marketable Securities - Additional Information (Detail)	12 Months Ended
Dec. 31, 2019 USD ($) position	Dec. 31, 2018 USD ($) position	Dec. 31, 2017 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Proceeds from sale of available-for-sale marketable securities		$ 79,808,000	$ 8,755,000
Realized (losses) gains		$ (5,000)	$ 5,000
Number of available-for-sale marketable securities in unrealized loss positions \| position	16	69
Total number of positions \| position	81	84
Other-than-temporary impairments on securities	$ 0	$ 0
Money Market Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Proceeds from sale of available-for-sale marketable securities	$ 0	79,808,000
Realized (losses) gains		$ (5,000)

Available for sale securities qualitative disclosure number of positions.

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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).

+ References

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-Publisher FASB
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Number of investments in debt securities measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Amount of other-than-temporary impairment (OTTI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), recognized in earnings and other comprehensive loss (OCI).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 8A
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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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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

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