DERIVATIVE INSTRUMENTS (Tables)

12 Months Ended

Dec. 31, 2015

DERIVATIVE INSTRUMENTS

Assumptions used in determining fair value of warrants

	Year Ended December 31,
	2015	2014	2013
Risk free interest rate	0.65%	1.47%	NA
Expected dividend yield	0%	0%	NA
Contractual term	3.4 years	4.4 years	NA
Expected volatility	100%	119%	NA

Changes in derivative warrant liability

	Year Ended December 31,
	2015			2014		2013
Balance at beginning of year	$	7,224		$	—	$	14,585
Issuance of warrants		—			6,848		—
Increase (decrease) in the fair value of the 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 year	$	1,907		$	7,224	$	—