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 |