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COMMON STOCK Restricted Stock - Market Based Awards Fair Value Assumptions (Details) - Restricted Stock - Market Based Awards [Member] - $ / shares
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected term of award 3 years 3 years  
Risk-free interest rate 0.90% 0.80%  
Expected Volatility 53.00% 55.20%  
Weighted-average grant date fair value per share $ 66.16 $ 56.87 $ 49.04