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ACCOUNTING POLICIES - The Company and Business Combinations and Divestitures Narrative (Details) $ in Thousands |  | 6 Months Ended |
--- | --- | --- | ---
Feb. 01, 2019 USD ($) shares | Jun. 30, 2019 USD ($) item | Jun. 30, 2018 USD ($) | Dec. 31, 2018 USD ($)
Business Acquisition [Line Items] |  |  |  |
Date when former legal or registered name was changed |  | May 17, 2019 |  |
Number of bank branches (branch) | item |  | 153 |  |
Number of ATMs (ATM) | item |  | 200 |  |
Cash paid in acquisition |  | $ 12 | $ 10,928 |
Goodwill |  | $ 930,449 |  | $ 727,168
Xenith |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Number of bank branches (branch) | item |  | 7 |  |
Access National Bank |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Fair value of total consideration transferred | $ 499,986 |  |  |
Number of shares equivalent to each share of acquired entity (shares) | shares | 0.75 |  |  |
Number of common shares issued (shares) | shares | 15,842,026 |  |  |
Cash paid in acquisition | $ 12 |  |  |
Goodwill | 203,265 |  |  |
Acquired amortizable intangible assets | $ 43,500 |  |  |
Minimum | Access National Bank |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Intangible assets, amortization period (years) | 5 years |  |  |
Maximum | Access National Bank |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Intangible assets, amortization period (years) | 10 years |  |  |

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