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ACCOUNTING POLICIES (Details) $ / shares in Units, $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2017 USD ($) $ / shares | Sep. 30, 2016 USD ($) $ / shares | Sep. 30, 2017 USD ($) Component Calculation Segment Factor $ / shares | Sep. 30, 2016 USD ($) $ / shares
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |
Number of broad components used in allowance methodology | Component |  |  | 2 |
Number of calculations used for general loan loss allocation | Calculation |  |  | 2 |
Number of main loan segments | Segment |  |  | 5 |
Period of historical net charge-off data for each loan class used in determining allowance level |  |  | 36 months |
Number of qualitative environmental factors used in qualitative calculation for loan loss allocation | Factor |  |  | 8 |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Net income | $ | $ 35,243 | $ 27,160 | $ 78,691 | $ 77,420
Net income per diluted common share (in dollars per share) | $ / shares | $ 0.68 | $ 0.61 | $ 1.60 | $ 1.74
Core Deposits [Member] | Minimum [Member] |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |
Intangible asset useful life (amortization period) |  |  | 7 years |
Core Deposits [Member] | Maximum [Member] |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |
Intangible asset useful life (amortization period) |  |  | 20 years |
Customer Relationships [Member] | Minimum [Member] |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |
Intangible asset useful life (amortization period) |  |  | 7 years |
Customer Relationships [Member] | Maximum [Member] |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |
Intangible asset useful life (amortization period) |  |  | 20 years |
Commercial Portfolio Segment [Member] | Minimum [Member] |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |
Threshold balance of loans individually evaluated for impairment | $ | $ 500 |  | $ 500 |
ASU 2016-09 [Member] |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Net income | $ | $ 300 |  | $ 2,900 |
Net income per diluted common share (in dollars per share) | $ / shares |  |  | $ 0.05 |
ASU 2016-09 [Member] | Maximum [Member] |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Net income per diluted common share (in dollars per share) | $ / shares | $ 0.01 |  |  |

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