Annual report pursuant to Section 13 and 15(d)

BORROWINGS (Narrative) (Details)

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BORROWINGS (Narrative) (Details)
$ in Thousands
 12 Months Ended
Jan. 01, 2014
USD ($)
Aug. 23, 2012
USD ($)
Dec. 31, 2017
USD ($)
acquisition
Dec. 31, 2016
USD ($)
Dec. 31, 2015
USD ($)
Subordinated Borrowing [Line Items]          
Remaining available balance for the federal funds lines     $ 227,000 $ 175,000  
Remaining borrowing capacity with correspondent banks     25,000 25,000  
Maximum collateral dependent line of credit with the FHLB     2,700,000 2,400,000  
Subordinated debt     150,000 150,000  
Prepayment penalty   $ 19,600      
Prepayment penalty amortization expense     1,900 $ 1,900 $ 1,800
Trust Preferred Capital Notes          
Subordinated Borrowing [Line Items]          
Trust preferred capital notes principal balance     90,500    
Subordinated Debt Notes          
Subordinated Borrowing [Line Items]          
Remaining fair value discount on acquired notes     $ 1,799    
Subordinated debt maturity date     Dec. 15, 2026    
Stated percentage on debt instrument       5.00%  
Remaining fair value premium on acquired FHLB advances     $ 130    
Acquisitions, Prior To 2006          
Subordinated Borrowing [Line Items]          
Number of bank acquisitions | acquisition     2    
LIBOR | Subordinated Debt Notes          
Subordinated Borrowing [Line Items]          
Three-month LIBOR rate plus     3.175%    
Acquisitions, Prior To 2006          
Subordinated Borrowing [Line Items]          
Trust preferred capital notes principal balance     $ 58,500    
StellarOne Bank          
Subordinated Borrowing [Line Items]          
Loans from other Federal Home Loan Banks $ 70,000   10,000    
StellarOne Bank | Trust Preferred Capital Notes          
Subordinated Borrowing [Line Items]          
Trust preferred capital notes principal balance $ 32,000        
Remaining fair value discount on acquired notes     $ 6,500