General - Investments - Amortized Cost (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Amortized cost
Amortized Cost	$ 356,557	$ 344,965
Gross Unrealized Gains	580	250
Gross Unrealized Losses	(656)	(58)
Estimated Fair Value	356,481	345,157
U.S. Government and agency securities
Amortized cost
Amortized Cost	90,166	104,096
Gross Unrealized Gains	554	75
Gross Unrealized Losses	(7)	(12)
Estimated Fair Value	90,713	104,159
Corporate debt securities
Amortized cost
Amortized Cost	265,086	239,564
Gross Unrealized Gains	26	175
Gross Unrealized Losses	(649)	(46)
Estimated Fair Value	264,463	239,693
Certificates of deposit
Amortized cost
Amortized Cost	1,305	1,305
Estimated Fair Value	$ 1,305	$ 1,305

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

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