MARKETABLE SECURITIES - Marketable Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Marketable securities	$ 199,083	$ 191,799
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Marketable securities	26,925	31,864
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities	132,647	125,547
Securities of government sponsored entities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities	$ 39,511	$ 34,388