INVESTMENTS (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Available-for-sale securities
Amortized cost	$ 1,138
Estimated fair value	1,448
Amortized cost
Due within one year	114
Due after one year through five years	546
Due after five years through ten years	478
Total	1,138
Estimated fair value
Due within one year	145
Due after one year through five years	685
Due after five years through ten years	618
Estimated fair value	1,448
U.S. Treasury Bonds
Available-for-sale securities
Amortized cost	1,138	$ 1,069
Gross unrealized gains	310	353
Estimated fair value	1,448	1,422
Amortized cost
Total	1,138	1,069
Estimated fair value
Estimated fair value	1,448	$ 1,422
U.S. Treasury Bonds, maturing 2020
Available-for-sale securities
Aggregate par value	1,600
U.S. Treasury Bonds, maturing 2022
Available-for-sale securities
Aggregate par value	$ 1,600