STOCKHOLDERS’ EQUITY / DEFICIT - Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Stockholders Equity [Line Items]
Proceeds exercise of warrants			$ 4,475,000	$ 8,398,000	$ 0
Value of shares repurchased during the period				$ 2,258,000	$ 957,000
Common Stock
Stockholders Equity [Line Items]
Closing stock price of stock options outstanding and exercisable (in dollars per share)			$ 19.29
Shares repurchased during the period (in shares)		130,790	0	248,801
Value of shares repurchased during the period		$ 957,272		$ 2,300,000
Retirement of treasury stock (in shares)	379,591		379,591
Stock Options
Stockholders Equity [Line Items]
Weighted average grant date fair value of options (in dollars per share)			$ 19.02	$ 8.56	$ 6.03
Unrecognized compensation cost associated with unvested options			$ 47,400,000
Weighted average period for unrecognized costs (in years)			1 year 10 months 24 days
Restricted shares
Stockholders Equity [Line Items]
Weighted average period for unrecognized costs (in years)			1 year 9 months 18 days
Unrecognized compensation cost related to restricted shares granted			$ 7,100,000
Warrants
Stockholders Equity [Line Items]
Number of common stock called by warrants (in shares)			870,306	1,947,377
Proceeds exercise of warrants			$ 4,500,000	$ 8,400,000
Reclassification of derivative liability as equity			23,500,000	$ 23,400,000
Change in fair value of warrants			$ 2,800,000