FAIR VALUE MEASUREMENTS - Unobservable Inputs (Level 3) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Fair Value Measurements Using Unobservable Inputs (Level 3)
Balance, beginning of period	$ (12,600)	$ (2,300)
Accretion expense (recognized in general and administrative expenses)		(235)
Total	$ (12,600)	$ (2,535)