Cash Equivalents and Marketable Securities - Schedule of Estimated Fair Value of Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Schedule Of Available For Sale Securities [Line Items]
Cash equivalents, amortized cost	$ 15,520	$ 19,407
Cash equivalents, gross unrealized losses		(1)
Cash equivalents, estimated fair value	15,520	19,406
Marketable securities, amortized cost	52,645	52,078
Marketable securities, gross unrealized gains	60
Marketable securities, gross unrealized losses	(9)	(26)
Marketable securities, estimated fair value	52,696	52,052
U.S. government securities
Schedule Of Available For Sale Securities [Line Items]
Marketable securities, amortized cost		4,114
Marketable securities, gross unrealized losses		(2)
Marketable securities, estimated fair value		4,112
Commercial paper
Schedule Of Available For Sale Securities [Line Items]
Cash equivalents, amortized cost	2,247	5,977
Cash equivalents, gross unrealized losses		(1)
Cash equivalents, estimated fair value	2,247	5,976
Marketable securities, amortized cost	12,931	47,964
Marketable securities, gross unrealized gains	15
Marketable securities, gross unrealized losses		(24)
Marketable securities, estimated fair value	12,946	47,940
Corporate bonds
Schedule Of Available For Sale Securities [Line Items]
Marketable securities, amortized cost	39,714
Marketable securities, gross unrealized gains	45
Marketable securities, gross unrealized losses	(9)
Marketable securities, estimated fair value	39,750
Money market funds
Schedule Of Available For Sale Securities [Line Items]
Cash equivalents, amortized cost	7,023	7,180
Cash equivalents, estimated fair value	7,023	7,180
Reverse repurchase agreements
Schedule Of Available For Sale Securities [Line Items]
Cash equivalents, amortized cost	6,250	6,250
Cash equivalents, estimated fair value	$ 6,250	$ 6,250

Cash equivalents unrealized losses.

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Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) 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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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) 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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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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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Amount of short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

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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.

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