FAIR VALUE MEASUREMENTS - Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Asset:
Marketable securities, available-for-sale	$ 199,083	$ 191,799
Recurring basis
Asset:
Marketable securities, available-for-sale	199,083	191,799
Liabilities:
Derivative liability related to warrants	24,470	38,810
Business combination-related contingent consideration	60,299	59,021
Recurring basis | Quoted prices in active markets (Level 1)
Asset:
Marketable securities, available-for-sale		0
Recurring basis | Significant other observable inputs (Level 2)
Asset:
Marketable securities, available-for-sale	199,083	191,799
Recurring basis | Significant unobservable inputs (Level 3)
Liabilities:
Derivative liability related to warrants	24,470	38,810
Business combination-related contingent consideration	$ 60,299	$ 59,021