Available-for-Sale-Securities - Summary of Available-for-Sale Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Cost	$ 22,766	$ 37,850
Gross Unrealized Gains	3	0
Gross Unrealized Losses	(1)	(32)
Estimated Fair Value	22,768	37,818
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Cost	11,673	33,536
Gross Unrealized Gains	3	0
Gross Unrealized Losses	(1)	(32)
Estimated Fair Value	11,675	33,504
Money market funds
Debt Securities, Available-for-sale [Line Items]
Cost	11,093	4,314
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	$ 11,093	$ 4,314

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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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
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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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