DERIVATIVE INSTRUMENTS (Tables)

12 Months Ended

Dec. 31, 2014

DERIVATIVE INSTRUMENTS

Assumptions used in determining fair value of warrants

	Year Ended December 31,
	2014	2013		2012
Risk free interest rate	1.47%		N/A	0.32 - 0.35%
Expected dividend yield	0%		N/A	0%
Contractual term	4.4 years		N/A	2.7 - 2.9 years
Expected volatility	119%		N/A	73%

Changes in derivative warrant liability

	Year Ended December 31,
	2014		2013			2012
Balance at beginning of year	$	—	$	14,585		$	35,473
Issuance of warrants		6,848		—			—
Increase (decrease) in the fair value of the warrants		376		18,871			(17,480	)
Fair value of derivative warrant liability reclassified to additional paid in capital		—		(33,456	)		(3,408	)
Balance at end of year	$	7,224	$	—		$	14,585