Fair Value Measurements - Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis and Level of Inputs used in such Measurements (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Assets
Cash and cash equivalents, Adjusted Cost	$ 133,245	$ 55,046
Fair Value Measurements Recurring
Assets
Cash and cash equivalents, Adjusted Cost	133,246	55,047
Cash and cash equivalents, Unrealized Losses	(1)	(1)
Cash and cash equivalents, Fair Value	133,245	55,046
Assets, Adjusted Cost	206,012	128,283
Assets, Unrealized Gains	56	21
Assets, Unrealized Losses	(5)	(15)
Assets, Fair Value	206,063	128,289
Fair Value Measurements Recurring \| Short-term Investments
Assets
Investments, Adjusted Cost	72,766	73,236
Investments, Unrealized Gains	56	21
Investments, Unrealized Losses	(4)	(14)
Investments, Fair Value	72,818	73,243
Fair Value Measurements Recurring \| Cash
Assets
Cash and cash equivalents, Adjusted Cost	2,494	1,271
Cash and cash equivalents, Fair Value	2,494	1,271
Fair Value Measurements Recurring \| Level 1 \| Money Market Funds
Assets
Cash and cash equivalents, Adjusted Cost	102,532	12,495
Cash and cash equivalents, Fair Value	102,532	12,495
Fair Value Measurements Recurring \| Level 2 \| Commercial Paper
Assets
Cash and cash equivalents, Adjusted Cost	26,520	41,281
Cash and cash equivalents, Unrealized Losses	(1)	(1)
Cash and cash equivalents, Fair Value	26,519	41,280
Fair Value Measurements Recurring \| Level 2 \| Commercial Paper \| Short-term Investments
Assets
Investments, Adjusted Cost	3,899	17,898
Investments, Unrealized Losses		(6)
Investments, Fair Value	3,899	17,892
Fair Value Measurements Recurring \| Level 2 \| U.S. Agency Securities
Assets
Cash and cash equivalents, Adjusted Cost	1,700
Cash and cash equivalents, Fair Value	1,700
Fair Value Measurements Recurring \| Level 2 \| U.S. Agency Securities \| Short-term Investments
Assets
Investments, Adjusted Cost	60,895	32,776
Investments, Unrealized Gains	47	20
Investments, Unrealized Losses	(4)	(2)
Investments, Fair Value	60,938	32,794
Fair Value Measurements Recurring \| Level 2 \| Corporate Debt Securities \| Short-term Investments
Assets
Investments, Adjusted Cost	7,972	13,953
Investments, Unrealized Gains	9	1
Investments, Unrealized Losses		(6)
Investments, Fair Value	$ 7,981	13,948
Fair Value Measurements Recurring \| Level 2 \| U.S. Government Securities \| Short-term Investments
Assets
Investments, Adjusted Cost		4,011
Investments, Fair Value		4,011
Fair Value Measurements Recurring \| Level 2 \| Asset-backed Securities \| Short-term Investments
Assets
Investments, Adjusted Cost		4,598
Investments, Fair Value		$ 4,598

Assets, amortized cost basis.

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Assets, gross unrealized gains.

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Assets, gross unrealized losses.

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Cash and cash equivalents, gross unrealized losses.

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Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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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 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. Excludes cash and cash equivalents within disposal group and discontinued operation.

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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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