Annual report pursuant to Section 13 and 15(d)

INTANGIBLE ASSETS (Narrative) (Details)

v3.8.0.1
INTANGIBLE ASSETS (Narrative) (Details) - USD ($)
 3 Months Ended 12 Months Ended
Jun. 30, 2017
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
May 31, 2016
Finite-Lived Intangible Assets [Line Items]          
Goodwill   $ 298,528,000 $ 298,191,000    
Impairment charges $ 0        
Intangible assets, amortization expense   $ 6,088,000 7,210,000 $ 8,445,000  
Core Deposits | Minimum          
Finite-Lived Intangible Assets [Line Items]          
Intangible assets, amortization period   4 years      
Core Deposits | Maximum          
Finite-Lived Intangible Assets [Line Items]          
Intangible assets, amortization period   14 years      
Other Intangible Assets          
Finite-Lived Intangible Assets [Line Items]          
Intangible assets, amortization expense     0 0  
Other Intangible Assets | Minimum          
Finite-Lived Intangible Assets [Line Items]          
Intangible assets, amortization period   5 years      
Other Intangible Assets | Maximum          
Finite-Lived Intangible Assets [Line Items]          
Intangible assets, amortization period   10 years      
Core Deposits and Other Intangible Assets          
Finite-Lived Intangible Assets [Line Items]          
Intangible assets, amortization expense   $ 6,100,000 $ 7,200,000 $ 8,400,000  
ODCM          
Finite-Lived Intangible Assets [Line Items]          
Goodwill         $ 4,700,000
Business combination, finite-lived intangibles         $ 4,500,000
ODCM | Minimum          
Finite-Lived Intangible Assets [Line Items]          
Intangible assets, amortization period   5 years      
ODCM | Maximum          
Finite-Lived Intangible Assets [Line Items]          
Intangible assets, amortization period   10 years