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ACCOUNTING POLICIES (Narrative) (Details) $ in Thousands |  |  | 3 Months Ended | 12 Months Ended
--- | --- | --- | --- | ---
Apr. 30, 2019 USD ($) | Feb. 01, 2019 USD ($) shares | Mar. 31, 2020 USD ($) item | Mar. 31, 2019 USD ($) | Dec. 31, 2019 USD ($)
Accounting Policies [Line Items] |  |  |  |  |
Number of bank branches | item |  |  | 149 |  |
Number of ATM's | item |  |  | 170 |  |
Impairment charges for goodwill | $ 0 |  | $ 0 |  |
Goodwill |  |  | 935,560 |  | $ 935,560
Loans held for investment, accrued interest receivable |  |  | 31,100 |  |
HTM securities, Accrued interest receivable |  |  | 5,200 |  |
Cash paid in acquisition |  |  | $ 0 | $ 12 |
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%
Minimum |  |  |  |  |
Accounting Policies [Line Items] |  |  |  |  |
Intangible assets, amortization period (years) |  |  | 4 years |  |
Maximum |  |  |  |  |
Accounting Policies [Line Items] |  |  |  |  |
Intangible assets, amortization period (years) |  |  | 10 years |  |
Access National Bank |  |  |  |  |
Accounting Policies [Line Items] |  |  |  |  |
Number of shares equivalent to each share of acquired entity | shares |  | 0.75 |  |  |
Company's common shares issued | shares |  | 15,842,026 |  |  |
Cash paid in acquisition |  | $ 12 |  |  |

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