Quarterly report pursuant to Section 13 or 15(d)

BORROWINGS (Narrative) (Details)

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BORROWINGS (Narrative) (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jan. 01, 2018
Jan. 01, 2014
Aug. 23, 2012
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Dec. 31, 2017
Dec. 31, 2016
Subordinated Borrowing [Line Items]                  
Remaining available balance for the federal funds lines       $ 237,000   $ 237,000   $ 227,000  
Remaining available balance of alternate line of credit       25,000   25,000   25,000  
Maximum collateral dependent line of credit with the FHLB       3,900,000   3,900,000   2,700,000  
Subordinated debt       158,500   158,500   150,000 $ 150,000
Prepayment penalty     $ 19,600            
Prepayment penalty amortization expense       490 $ 478 971 $ 947    
Trust Preferred Capital Notes                  
Subordinated Borrowing [Line Items]                  
Trust preferred capital notes principal balance           145,500      
Remaining fair value discount on acquired notes       16,000   16,000      
Subordinated Debt                  
Subordinated Borrowing [Line Items]                  
Remaining fair value discount on acquired notes       1,700   $ 1,700   $ 1,800  
Fixed interest rate on debt instrument                 5.00%
Subordinated Debt | LIBOR                  
Subordinated Borrowing [Line Items]                  
Spread on LIBOR           3.175%      
Acquisitions, Prior To 2006                  
Subordinated Borrowing [Line Items]                  
Trust preferred capital notes principal balance           $ 58,500      
StellarOne                  
Subordinated Borrowing [Line Items]                  
Long-term FHLB borrowings   $ 70,000   10,000   10,000      
Remaining fair value premium on acquired FHLB advances       19   19      
StellarOne | Trust Preferred Capital Notes                  
Subordinated Borrowing [Line Items]                  
Trust preferred capital notes principal balance   $ 32,000              
Xenith                  
Subordinated Borrowing [Line Items]                  
Trust preferred capital notes principal balance $ 55,000                
Subordinated debt 8,500                
Xenith | Trust Preferred Capital Notes                  
Subordinated Borrowing [Line Items]                  
Remaining fair value discount on acquired notes 9,900                
Xenith | Subordinated Debt                  
Subordinated Borrowing [Line Items]                  
Remaining fair value discount on acquired notes $ 259     $ 207   $ 207      
Fixed interest rate on debt instrument 6.75%