Marketable Securities - Schedule of Amortized Cost and Estimated Fair Value of Marketable Securities Classified by Maturity Date (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Available For Sale Securities Debt Maturities Fair Value [Abstract]
Amortized Cost, Due within one year	$ 53,277	$ 47,767
Amortized Cost, Due after one through five years	14,376	14,914
Amortized Cost, Due after five through ten years	0	0
Amortized Cost, Due after ten years	0	0
Amortized Cost, Total marketable securities	67,653	62,681
Fair Value, Due within one year	53,366	47,732
Fair Value, Due after one through five years	14,526	14,952
Fair Value, Due after five through ten years	0	0
Fair Value, Due after ten years	0	0
Fair Value, Total marketable securities	$ 67,892	$ 62,684

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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