SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Schedule of Cash, Cash Equivalents, and Short Term Investments) (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Cash And Cash Equivalents [Line Items]
Cost	$ 66,496	$ 33,546
Gross Unrealized Gains	72	69
Gross Unrealized Losses	(127)	(119)
Estimated fair value	66,441	33,496
Cash [Member]
Cash And Cash Equivalents [Line Items]
Cost	37,837	9,166
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated fair value	37,837	9,166
Money market funds [Member]
Cash And Cash Equivalents [Line Items]
Cost	180	457
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated fair value	180	457
Government and agency securities [Member]
Cash And Cash Equivalents [Line Items]
Cost	22,903	19,132
Gross Unrealized Gains	57	51
Gross Unrealized Losses	(108)	(96)
Estimated fair value	22,852	19,087
Corporate debt securities [Member]
Cash And Cash Equivalents [Line Items]
Cost	5,576	4,791
Gross Unrealized Gains	15	18
Gross Unrealized Losses	(19)	(23)
Estimated fair value	$ 5,572	$ 4,786