| 
           ACQUISITIONS (Summary of Acquisition-Related Expenses) (Details) (USD $) 
        In Thousands, unless otherwise specified  | 
        3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
| 
           Sep. 30, 2014 
         | 
        
           Sep. 30, 2013 
         | 
        
           Sep. 30, 2014 
         | 
        
           Sep. 30, 2013 
         | 
      |
| Business Combination, Separately Recognized Transactions [Line Items] | ||||
| Salaries and employee benefits | $ 26,060 | $ 17,416 | $ 83,726 | $ 53,294 | 
| Professional services | 1,400 | 795 | 3,897 | 2,183 | 
| Total | 1,695 | 473 | 19,524 | 1,393 | 
| 
           StellarOne Bank [Member] 
         | 
        ||||
| Business Combination, Separately Recognized Transactions [Line Items] | ||||
| Salaries and employee benefits | 200 | 7,878 | ||
| Professional services | 122 | 473 | 3,717 | 1,393 | 
| Other costs of operations | 1,373 | 7,929 | ||
| Total | $ 1,695 | $ 473 | $ 19,524 | $ 1,393 | 
| X | ||||||||||
| 
             
- Definition 
          This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, severance and employee-related charges, systems integrations; and other related charges as well as other restructuring charges. No definition available. 
  | 
        
| X | ||||||||||
| 
             
- Details 
          
  | 
        
| X | ||||||||||
| 
             
- Definition 
          The aggregate amount of expenditures for salaries, wages, profit sharing and incentive compensation, and other employee benefits, including equity-based compensation, and pension and other postretirement benefit expense. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          This element represents a sum total of expenses not separately reflected on the income statement for the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          A fee charged for services from professionals such as doctors, lawyers and accountants. The term is often expanded to include other professions, for example, pharmacists charging to maintain a medicinal profile of a client or customer. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
  |