Cash, Cash Equivalents and Investments - Fair value and Amortized cost (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Cash and Cash Equivalents, at Carrying Value	$ 92,183	$ 157,954
Cash, cash equivalents and money market funds
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	86,473	157,954
Estimated Fair Value	86,473	157,954
U.S. Treasury securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	31,017	20,037
Gross Unrealized Gains	200	16
Estimated Fair Value	31,217	20,053
Commercial paper
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	19,543
Estimated Fair Value	19,543
Corporate debt securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	16,436	3,459
Gross Unrealized Losses	36
Estimated Fair Value	16,400	3,459
U.S. Agency bonds
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	10,000
Gross Unrealized Gains	15
Estimated Fair Value	10,015
Certificates of deposit
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	2,644	1,950
Estimated Fair Value	2,644	1,950
Total
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	166,113	183,400
Gross Unrealized Gains	215	16
Gross Unrealized Losses	36
Estimated Fair Value	166,292	183,416
Less amounts classified as cash and cash equivalents
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	92,183	157,954
Estimated Fair Value	92,183	157,954
Total available-for-sale investments
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	73,930	25,446
Gross Unrealized Gains	215	16
Gross Unrealized Losses	36
Estimated Fair Value	$ 74,109	$ 25,462

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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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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