FEDERAL HOME LOAN BANK ADVANCES - FHLB ADVANCES (Details) - USD ($)
3 Months Ended 12 Months Ended
Sep. 30, 2016
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
FHLB advances        
Total FHLB advances   $ 802,500,000 $ 699,500,000  
Interest rate (as percent)   1.35%    
FHLB advance prepayment penalty   $ 846,000 0 $ 0
FHLB advances payoff $ 50,000,000      
Additional collateralized advances available   378,000,000 567,000,000  
Overnight advance        
FHLB advances        
Total FHLB advances   285,000,000 150,000,000  
Variable interest rate advance indexed to 3-Month LIBOR plus 0.14% due on December 20, 2017        
FHLB advances        
Total FHLB advances   $ 10,000,000 $ 10,000,000  
Variable interest rate advance indexed to 3-Month LIBOR plus 0.14% due on December 20, 2017 | London Interbank Offered Rate (LIBOR)        
FHLB advances        
Interest rate (as percent)   0.14% 0.14%  
Fixed interest rate advances with a weighted average interest rate of 1.64% due through 2023        
FHLB advances        
Total FHLB advances   $ 457,500,000 $ 439,500,000  
Interest rate (as percent)   1.46% 1.46%  
Putable fixed interest rate advances with a weighted average interest rate of 4.39% due through 2017        
FHLB advances        
Total FHLB advances   $ 50,000,000 $ 100,000,000  
Interest rate (as percent)   4.39% 4.39%  
FHLB advances payoff   $ 50,000,000    
Various other unsecured lines of credit        
FHLB advances        
Unsecured lines of credit   $ 150,000,000 $ 170,000,000