Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 25
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Fair Value	25
Amortized Cost		$ 8,320
Gross Unrealized Gains		0
Gross Unrealized Losses		(1)
Fair Value		8,319
Money market mutual funds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	25
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Fair Value	$ 25
Amortized Cost		7,318
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Fair Value		7,318
United States treasuries
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		1,002
Gross Unrealized Gains		0
Gross Unrealized Losses		(1)
Fair Value		$ 1,001

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
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-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).

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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
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-Section 50
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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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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 security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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