INVESTMENTS - Cost and Carrying Amounts of Available-For-Sale Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt securities: corporate bonds
Cost	$ 700	$ 4,306
Gross Unrealized Gains	6	82
Gross Unrealized Losses	(22)	(6)
Carrying Value	684	4,382
Marketable equity securities
Cost	513	10,400
Gross Unrealized Gains	710	10,327
Gross Unrealized Losses	(5)	(38)
Carrying Value	1,218	20,689
Total
Cost	1,213	14,706
Gross Unrealized Gains	716	10,409
Gross Unrealized Losses	(27)	(44)
Carrying Value	$ 1,902	$ 25,071

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in equity securities classified as available-for-sale.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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