Cash Equivalents and Investments (Schedule of Estimated Fair Value of Available-for-Sale Securities) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Schedule of Available-for-sale Securities [Line Items]
Estimated Market Value	$ 22,624	$ 18,461
Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Due within one year	3,740
Amortized Cost, Due after one year through five years	355
Amortized Cost	4,095
Estimated Market Value, Due within one year	3,748
Estimated Market Value, Due after one year through five years	355
Estimated Market Value	$ 4,103	$ 9,700

Amortized cost 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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