EQUITY-BASED COMPENSATION - Summary of assumptions to estimate the grant date fair value of stock options and SARs (Details) (Stock Option And Stock Appreciation Rights)
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Stock Option And Stock Appreciation Rights
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected volatility, Minimum 53.40% 55.90% 66.60%
Expected volatility, Maximum 69.90% 72.40% 77.10%
Weighted-average volatility 67.70% 67.80% 72.30%
Expected term (in years) 6 years 1 month 6 days 6 years 3 months 18 days 5 years 6 months
Risk-free rate 1.51% 1.03% 1.91%
Dividend yield 0.00% 0.00% 0.00%