SHORT-TERM INVESTMENTS (Details 4) - Jun. 30, 2015 - USD ($) $ in Thousands	Total
SHORT-TERM INVESTMENTS
Estimated Fair Value	$ 530,252
Gross Unrealized Losses	(1,675)
Corporate notes and bonds
SHORT-TERM INVESTMENTS
Estimated Fair Value	409,095
Gross Unrealized Losses	(1,591)
U.S. agency obligations
SHORT-TERM INVESTMENTS
Estimated Fair Value	52,770
Gross Unrealized Losses	(61)
U.S. treasury securities
SHORT-TERM INVESTMENTS
Estimated Fair Value	26,506
Gross Unrealized Losses	(5)
Commercial paper
SHORT-TERM INVESTMENTS
Estimated Fair Value	39,242
Gross Unrealized Losses	(17)
Certificate of deposit
SHORT-TERM INVESTMENTS
Estimated Fair Value	2,639
Gross Unrealized Losses	$ (1)