Quarterly report pursuant to Section 13 or 15(d)

SECURITIES (Narrative) (Details)

v3.10.0.1
SECURITIES (Narrative) (Details)
 3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2018
USD ($)
security
Jun. 30, 2018
USD ($)
security
Dec. 31, 2017
USD ($)
security
Schedule of Investments [Line Items]      
Individual Available-for-sale securities that had been in a continuous loss position for more than 12 months, amount $ 182,813,000 $ 182,813,000 $ 197,640,000
Available-for-sale securities that had been in a continuous loss position for more than 12 months, unrealized loss 6,334,000 6,334,000 4,188,000
Held to maturity securities unrealized gains before tax   $ 105,000 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 52,400,000 $ 52,400,000 $ 27,600,000
Federal Home Loan Bank stock 52,400,000 $ 52,400,000 $ 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 75 75 71
Accounting Standards Update 2017-12      
Schedule of Investments [Line Items]      
Securities, available-for-sale   $ 187,400,000