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BORROWINGS (Narrative) (Details) - USD ($) |  |  | 3 Months Ended | 6 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | --- | ---
Feb. 01, 2019 | Aug. 23, 2012 | Jun. 30, 2019 | Jun. 30, 2018 | Jun. 30, 2019 | Jun. 30, 2018 | Dec. 31, 2018 | Jan. 01, 2018 | Dec. 31, 2016
Subordinated Borrowing [Line Items] |  |  |  |  |  |  |  |  |
Remaining available balance for the federal funds lines |  |  | $ 557,000,000.0 |  | $ 557,000,000.0 |  | $ 382,000,000.0 |  |
Remaining available balance of alternate line of credit |  |  | 25,000,000.0 |  | 25,000,000.0 |  | 25,000,000.0 |  |
Maximum collateral dependent line of credit with the FHLB |  |  | 5,100,000,000 |  | 5,100,000,000 |  | 4,000,000,000.0 |  |
Subordinated debt |  |  | 158,500,000 |  | 158,500,000 |  |  |  | $ 150,000,000.0
Prepayment penalty |  | $ 19,600,000 |  |  |  |  |  |  |
Prepayment penalty amortization expense |  |  | 501,562 | $ 490,000 | 994,000 | $ 971,000 |  |  |
Trust Preferred Capital Notes |  |  |  |  |  |  |  |  |
Subordinated Borrowing [Line Items] |  |  |  |  |  |  |  |  |
Trust preferred capital notes principal balance |  |  |  |  | 150,500,000 |  |  |  |
Remaining fair value discount on acquired notes |  |  | 15,300,000 |  | 15,300,000 |  |  |  |
Subordinated Debt |  |  |  |  |  |  |  |  |
Subordinated Borrowing [Line Items] |  |  |  |  |  |  |  |  |
Remaining fair value discount on acquired notes |  |  | 1,500,000 |  | $ 1,500,000 |  | $ 1,600,000 |  |
Fixed interest rate on debt instrument |  |  |  |  |  |  |  |  | 5.00%
Maturity Date |  |  |  |  | Dec. 15, 2026 |  |  |  |
Subordinated Debt | LIBOR |  |  |  |  |  |  |  |  |
Subordinated Borrowing [Line Items] |  |  |  |  |  |  |  |  |
Spread on LIBOR |  |  |  |  | 3.175% |  |  |  |
Acquisitions, Prior To 2006 |  |  |  |  |  |  |  |  |
Subordinated Borrowing [Line Items] |  |  |  |  |  |  |  |  |
Trust preferred capital notes principal balance |  |  |  |  | $ 58,500,000 |  |  |  |
Stellarone and Xenith | Trust Preferred Capital Notes |  |  |  |  |  |  |  |  |
Subordinated Borrowing [Line Items] |  |  |  |  |  |  |  |  |
Trust preferred capital notes principal balance |  |  |  |  | 87,000,000.0 |  |  |  |
Access National Bank |  |  |  |  |  |  |  |  |
Subordinated Borrowing [Line Items] |  |  |  |  |  |  |  |  |
Trust preferred capital notes principal balance | $ 5,000,000.0 |  |  |  |  |  |  |  |
Xenith |  |  |  |  |  |  |  |  |
Subordinated Borrowing [Line Items] |  |  |  |  |  |  |  |  |
Subordinated debt |  |  |  |  |  |  |  | $ 8,500,000 |
Xenith | Subordinated Debt |  |  |  |  |  |  |  |  |
Subordinated Borrowing [Line Items] |  |  |  |  |  |  |  |  |
Remaining fair value discount on acquired notes |  |  | $ 103,000 |  | $ 103,000 |  |  | $ 259,000 |
Fixed interest rate on debt instrument |  |  |  |  |  |  |  | 6.75% |

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