FAIR VALUE MEASUREMENTS FAIR VALUE MEASUREMENTS - Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	$ 231,452	$ 297,981
Long-term investments	15,217	2,187
Fair Value, Measurements, Recurring [Member] | Reported Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	28,072	34,980
Short-term investments	231,452	297,981
Long-term investments	15,217	2,187
Fair Value, Measurements, Recurring [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	28,072	34,980
Short-term investments	231,452	297,981
Long-term investments	$ 15,217	$ 2,187