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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 2) (USD $)
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Property and equipment    
Maturity period from date of purchase, short-term investments classified as cash equivalents, less than (in days) 91 days  
Capitalized software costs written-off   $ 4,900,000
Net book value 270,512,000 259,588,000
Buildings and leasehold improvements | Minimum
   
Property and equipment    
Estimated useful lives, minimum (in years) 3 years  
Buildings and leasehold improvements | Maximum
   
Property and equipment    
Estimated useful lives, minimum (in years) 39 years  
Capitalized internal use software
   
Property and equipment    
Net book value $ 33,400,000 $ 29,200,000
Capitalized internal use software | Minimum
   
Property and equipment    
Estimated useful lives, minimum (in years) 2 years  
Capitalized internal use software | Maximum
   
Property and equipment    
Estimated useful lives, minimum (in years) 3 years  
Furniture and other equipment | Minimum
   
Property and equipment    
Estimated useful lives, minimum (in years) 3 years  
Furniture and other equipment | Maximum
   
Property and equipment    
Estimated useful lives, minimum (in years) 10 years