Significant Accounting Policies - Cash, Cash Equivalents and Short-term Deposits (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Cash and Cash Equivalents
Significant Accounting Policies [Line Items]
Amortized Cost	$ 4,789	$ 2,594
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	4,789	2,594
Cash and Cash Equivalents \| Money Market Funds
Significant Accounting Policies [Line Items]
Amortized Cost	4,789	2,594
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	4,789	2,594
Marketable Securities
Significant Accounting Policies [Line Items]
Amortized Cost	41,510	39,776
Gross Unrealized Gains	23
Gross Unrealized Losses	(2)	(6)
Fair Value	41,531	39,770
Marketable Securities \| US Treasury securities
Significant Accounting Policies [Line Items]
Amortized Cost	41,510	39,776
Gross Unrealized Gains	23
Gross Unrealized Losses	(2)	(6)
Fair Value	41,531	39,770
Short-term Deposits
Significant Accounting Policies [Line Items]
Amortized Cost	10,000	70,438
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	10,000	70,438
Short-term Deposits \| Term Bank Deposits
Significant Accounting Policies [Line Items]
Amortized Cost	10,000	70,438
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	$ 10,000	$ 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).

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-Section 50
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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).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
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-Publisher FASB
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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).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454

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