Investments - Available-for-sale Securities by Security Type (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Unrealized Gains	$ 216	$ 60
Unrealized Losses	(72)	(6)
Cash equivalents, short-term and long-term investments, carrying value	148,430	170,390
Cash equivalents, short-term and long-term investments, fair vale disclosure	148,574	170,444
Short-term Investments
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Unrealized Gains	208	58
Unrealized Losses	(72)	(6)
Total cash equivalents and short-term investments, carrying value	146,830	168,791
Total cash equivalents and short-term investments, fair value	146,966	168,843
Short-term Investments \| Corporate debt securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Available-for-sale debt securities, amortized cost basis	31,825	46,695
Unrealized Gains	5	8
Unrealized Losses	(72)	(4)
Available-for-sale debt securities, fair value	31,758	46,699
Short-term Investments \| US Treasury Securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Available-for-sale debt securities, amortized cost basis	40,594	59,058
Unrealized Gains	161	26
Unrealized Losses	0	(2)
Available-for-sale debt securities, fair value	40,755	59,082
Short-term Investments \| Government agency securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Available-for-sale debt securities, amortized cost basis	8,420	12,796
Unrealized Gains	42	24
Unrealized Losses	0	0
Available-for-sale debt securities, fair value	8,462	12,820
Long-term Investments
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Available-for-sale debt securities, amortized cost basis	1,600	1,599
Unrealized Gains	8	2
Unrealized Losses	0	0
Available-for-sale debt securities, fair value	1,608	1,601
Long-term Investments \| Corporate debt securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Available-for-sale debt securities, amortized cost basis	1,600	1,599
Unrealized Gains	8	2
Unrealized Losses	0	0
Available-for-sale debt securities, fair value	1,608	1,601
Money market funds, included in cash equivalents
Debt Securities, Available-for-sale [Line Items]
Cash equivalents at carrying value	65,991	50,242
Cash equivalents at fair value	$ 65,991	$ 50,242

Cash Equivalents, Short-term and Long-Term Investments, Carrying Value

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Cash Equivalents, Short-term and Long-Term Investments, Fair Vale Disclosure

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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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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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