SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Available-for-sale Investments) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 83,866	$ 114,492
Gross unrealized loss	105	45
Gross unrealized gains	8	128
Estimated fair market value	83,769	114,575
Investments due in Less than 3 months [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	38,586
Gross unrealized loss	10
Gross unrealized gains	7
Estimated fair market value	38,583
Investments due in 4-12 months [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	33,654	30,233
Gross unrealized loss	36	0
Gross unrealized gains	1	36
Estimated fair market value	33,619	30,269
Investments due in more than 12 months [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	11,626	84,259
Gross unrealized loss	59	45
Gross unrealized gains	0	92
Estimated fair market value	11,567	84,306
Corporate securities [Member] | Investments due in Less than 3 months [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	38,586
Gross unrealized loss	10
Gross unrealized gains	7
Estimated fair market value	38,583
Corporate securities [Member] | Investments due in 4-12 months [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	33,654	30,233
Gross unrealized loss	36	0
Gross unrealized gains	1	36
Estimated fair market value	33,619	30,269
Corporate securities [Member] | Investments due in more than 12 months [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	11,626	84,259
Gross unrealized loss	59	45
Gross unrealized gains	0	92
Estimated fair market value	$ 11,567	$ 84,306