DERIVATIVE INSTRUMENTS - CHANGES IN DERIVATIVE WARRANT LIABILITY (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Changes in derivative warrant liability
Balance at beginning of year	$ 7,224		$ 14,585
Issuance of warrants		$ 6,848
Increase (decrease) in fair value of warrants	10,804	376	18,871
Fair value of derivative warrant liability reclassified to additional paid in capital	(16,121)		$ (33,456)
Balance at end of period	$ 1,907	$ 7,224