Fair Value Measurements - Available For Sale (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Fair value of available for sale marketable securities
Amortized Cost	$ 66,820	$ 75,435
Gross Unrealized Gains	11
Gross Unrealized Losses		(34)
Fair Value	66,831	75,401
U.S. Government agency securities
Fair value of available for sale marketable securities
Amortized Cost	39,355	49,124
Gross Unrealized Gains	8
Gross Unrealized Losses		(27)
Fair Value	39,363	49,097
Corporate debt obligations
Fair value of available for sale marketable securities
Amortized Cost	27,465	26,311
Gross Unrealized Gains	3
Gross Unrealized Losses		(7)
Fair Value	$ 27,468	$ 26,304

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

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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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 320
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-Section 45
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