Cash, Cash Equivalents and Short-term Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Cash and cash equivalents \| Money market funds
Amortized Cost	$ 8,815	$ 2,594
Gross Unrealized Gains	0	0
Gross Unrealized Loss	0	0
Fair Value	8,815	2,594
Cash and cash equivalents \| Cash
Amortized Cost	8,815	2,594
Gross Unrealized Gains	0	0
Gross Unrealized Loss	0	0
Fair Value	8,815	2,594
Marketable securities
Amortized Cost	37,837	39,776
Gross Unrealized Gains	5	0
Gross Unrealized Loss	0	(6)
Fair Value	37,842	39,770
Marketable securities \| US Treasury securities
Amortized Cost	37,837	39,776
Gross Unrealized Gains	5	0
Gross Unrealized Loss	0	(6)
Fair Value	37,842	39,770
Short-term investments
Amortized Cost	61,328	70,438
Gross Unrealized Gains	0	0
Gross Unrealized Loss	0	0
Fair Value	61,328	70,438
Short-term investments \| Term bank deposits
Amortized Cost	61,328	70,438
Gross Unrealized Gains	0	0
Gross Unrealized Loss	0	0
Fair Value	$ 61,328	$ 70,438

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).

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)
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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).

+ References

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 (c)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

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- Definition

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

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Amount of investment in debt security measured at amortized cost (held-to-maturity), investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale) and investment in debt security measured at fair value with change in fair value recognized in net income (trading).

+ References

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