Significant Accounting Policies (Details 1) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Amortized cost	$ 48,008	$ 49,718
Gross unrealized gains	0	0
Gross unrealized losses	(20)	(69)
Fair value	47,988	49,649
Commercial Paper [Member]
Amortized cost	2,426	3,986
Gross unrealized gains	0	0
Gross unrealized losses	(1)	(66)
Fair value	2,425	3,985
Corporate Debt Securities [Member]
Amortized cost	15,465	14,899
Gross unrealized gains	0	0
Gross unrealized losses	(19)	(1)
Fair value	15,446	14,833
US Government Agencies Debt Securities [Member]
Amortized cost	998	6,976
Gross unrealized gains	0	0
Gross unrealized losses	0	(1)
Fair value	998	6,975
Short-term Investments [Member]
Amortized cost	18,423	24,536
Gross unrealized gains	0	0
Gross unrealized losses	(19)	(69)
Fair value	18,404	24,467
Cash [Member]
Amortized cost	6,445	8,391
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Fair value	6,445	8,391
Money Market Funds [Member]
Amortized cost	22,211	14,295
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Fair value	22,211	14,295
Certificates of Deposit [Member]
Amortized cost	463	1,171
Gross unrealized gains	0	0
Gross unrealized losses	0	(1)
Fair value	463	1,170
Cash Equivalents [Member]
Amortized cost	29,585	25,182
Gross unrealized gains	0	0
Gross unrealized losses	(1)	0
Fair value	$ 29,584	$ 25,182

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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- Definition

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as 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 (b)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

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- Definition

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

+ References

No definition available.

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- Definition

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+ References

No definition available.

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