Cash and Cash Equivalents and Investments (Details 1) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Cash and Cash Equivalents
Fair Value
Amortized Cost	$ 55,592	$ 36,112
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	55,592	36,112
U.S. Treasury Securities
Fair Value
Amortized Cost	192,685	235,463
Gross Unrealized Gains	860	94
Gross Unrealized Losses		(10)
Estimated Fair Value	193,545	235,547
Total Short-term Investments
Fair Value
Amortized Cost	192,685	235,463
Gross Unrealized Gains	860	94
Gross Unrealized Losses	0	(10)
Estimated Fair Value	193,545	235,547
Total Cash and Cash Equivalents and Investments
Fair Value
Amortized Cost	248,277	271,575
Gross Unrealized Gains	860	94
Gross Unrealized Losses	0	(10)
Estimated Fair Value	$ 249,137	$ 271,659

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Amount of investment in debt and equity securities categorized neither as trading securities nor held-to-maturity securities and intended be sold or mature one year or operating cycle, if longer.

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