ACQUISITIONS (Business Acquisition, Pro Forma Information) (Details) - Access National Bank - USD ($) $ / shares in Units, $ in Thousands  | 
12 Months Ended | ||
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Dec. 31, 2019  | 
Dec. 31, 2018  | 
Dec. 31, 2017  | 
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| Business Acquisition [Line Items] | |||
| Total revenues | $ 681,306 | $ 666,921 | $ 468,840 | 
| Net income | $ 217,075 | $ 185,698 | $ 91,270 | 
| Earnings per share (in dollars per share) | $ 2.53 | $ 2.28 | $ 1.59 | 
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available. 
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- Definition The pro forma basic net income per share for a period as if the business combination or combinations had been completed at the beginning of a period. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef 
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- Definition The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Definition The pro forma revenue for a period as if the business combination or combinations had been completed at the beginning of the period. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Details 
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