Quarterly report pursuant to Section 13 or 15(d)

SECURITIES (Narrative) (Details)

v3.10.0.1
SECURITIES (Narrative) (Details)
 3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2018
USD ($)
security
Sep. 30, 2018
USD ($)
security
Dec. 31, 2017
USD ($)
security
Jun. 29, 2018
shares
Schedule of Investments [Line Items]        
Individual Available-for-sale securities that had been in a continuous loss position for more than 12 months, amount $ 292,110,000 $ 292,110,000 $ 197,640,000  
Available-for-sale securities that had been in a continuous loss position for more than 12 months, unrealized loss 11,787,000 11,787,000 4,188,000  
Held to maturity securities unrealized gains before tax   $ 125,000 3,600,000  
Individual held-to-maturity securities in continuous loss position for more than 12 months     $ 1,100,000  
Number of held-to-maturity securities in unrealized loss positions | security     2  
Held-to-maturity securities, continuous unrealized loss position, more than 12 months     $ 31,000  
Federal Home Loan Bank requires Bank to maintain percentage of stock equal to outstanding borrowings   4.25% 4.25%  
Percentage of Federal Reserve Bank of Richmond reserve   6.00% 6.00%  
Restricted equity securities consist of Federal Reserve Bank stock 52,600,000 $ 52,600,000 $ 27,600,000  
Federal Home Loan Bank stock 59,800,000 $ 59,800,000 $ 47,700,000  
Credit-related OTTI $ 0      
Available-for-sale Securities        
Schedule of Investments [Line Items]        
Number of available-for-sale securities that had been in a continuous loss position | security 108 108 71  
Accounting Standards Update 2017-12        
Schedule of Investments [Line Items]        
Securities, available-for-sale   $ 187,400,000    
Shore Premier        
Schedule of Investments [Line Items]        
Amount of shares received in transaction | shares       1,250,000
Fair value of purchasing company's stock $ 27,400,000 $ 27,400,000