Annual report pursuant to Section 13 and 15(d)

SECURITIES (Narrative) (Details)

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SECURITIES (Narrative) (Details)
 3 Months Ended 12 Months Ended
Jun. 30, 2018
USD ($)
Dec. 31, 2019
USD ($)
security
Dec. 31, 2018
USD ($)
security
Schedule of Investments [Line Items]      
Available for sale securities that had been in a continuous loss position for more than 12 months   $ 75,000,000.0 $ 385,400,000
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, accumulated loss   $ 696,000 $ 10,184,000
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   $ 67,000,000.0 $ 52,600,000
Federal Home Loan Bank Stock   63,900,000 72,000,000.0
Credit-related OTTI   $ 0 $ 0
Available-for-sale Securities      
Schedule of Investments [Line Items]      
Available for sale securities that had been in a continuous loss position | security   47 138
Accounting Standards Update 2017-12      
Schedule of Investments [Line Items]      
Available for sale debt securities, transfer, amount $ 187,400,000