LOANS AND ALLOWANCE FOR LOAN LOSSES - Allowance for Loan Losses and Recorded Investment By Portfolio Segment - (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Allowance for loan losses            
Balance at the beginning of the period $ 22,020 $ 23,250 $ 27,609      
Provision charged to expense 1,705 1,625 1,500      
Losses charged off (6,415) (7,392) (11,018)      
Ending Balance acquired with deteriorated credit 5,189 4,537 5,159      
Balance at the end of the period 22,499 22,020 23,250      
Ending Balance individually evaluated for impairment       $ 1,800 $ 1,429 $ 1,050
Ending Balance collectively evaluated for impairment       20,699 20,591  
Ending Balance acquired with deteriorated credit quality 8,954          
Total ending allowance balance 22,020 23,250 27,609 22,499 22,020 23,250
Loans            
Ending Balance individually evaluated for impairment       21,197 18,989  
Ending Balance collectively evaluated for impairment       2,621,522 2,136,403  
Total ending loan balance excluding accrued interest       2,651,673 2,155,392  
Accrued interest       7,342 5,878  
Allowance that includes a probability of default for subject loans 2,697 1,583        
Purchased credit impaired loans       8,954 212  
Commercial            
Allowance for loan losses            
Balance at the beginning of the period 6,511 2,977 3,291      
Provision charged to expense 3,166 4,010 (1,204)      
Losses charged off (682) (978) (241)      
Ending Balance acquired with deteriorated credit 659 502 1,131      
Balance at the end of the period 9,654 6,511 2,977      
Ending Balance individually evaluated for impairment       898 92  
Ending Balance collectively evaluated for impairment       8,756 6,419  
Total ending allowance balance 6,511 2,977 3,291 9,654 6,511 2,977
Loans            
Ending Balance individually evaluated for impairment       2,705 812  
Ending Balance collectively evaluated for impairment       531,854 444,852  
Total ending loan balance excluding accrued interest       534,559 445,664  
Commercial Real Estate            
Allowance for loan losses            
Balance at the beginning of the period 10,702 15,605 20,210      
Provision charged to expense (3,540) (6,118) (1,284)      
Losses charged off (663) (727) (5,583)      
Ending Balance acquired with deteriorated credit 1,207 1,942 2,262      
Balance at the end of the period 7,706 10,702 15,605      
Ending Balance individually evaluated for impairment       755 1,166  
Ending Balance collectively evaluated for impairment       6,951 9,536  
Ending Balance acquired with deteriorated credit quality 7,256          
Total ending allowance balance 10,702 15,605 20,210 7,706 10,702 15,605
Loans            
Ending Balance individually evaluated for impairment       7,904 8,909  
Ending Balance collectively evaluated for impairment       1,147,536 916,975  
Total ending loan balance excluding accrued interest       1,162,696 925,884  
Residential            
Allowance for loan losses            
Balance at the beginning of the period 3,859 3,501 3,409      
Provision charged to expense 1,318 2,115 1,977      
Losses charged off (1,345) (2,094) (2,295)      
Ending Balance acquired with deteriorated credit 415 337 410      
Balance at the end of the period 4,247 3,859 3,501      
Ending Balance individually evaluated for impairment       147 171  
Ending Balance collectively evaluated for impairment       4,100 3,688  
Ending Balance acquired with deteriorated credit quality 1,698          
Total ending allowance balance 3,859 3,501 3,409 4,247 3,859 3,501
Loans            
Ending Balance individually evaluated for impairment       10,458 9,155  
Ending Balance collectively evaluated for impairment       880,357 717,918  
Total ending loan balance excluding accrued interest       892,513 727,073  
Consumer            
Allowance for loan losses            
Balance at the beginning of the period 948 1,167 699      
Provision charged to expense 761 1,618 2,011      
Losses charged off (3,725) (3,593) (2,899)      
Ending Balance acquired with deteriorated credit 2,908 1,756 1,356      
Balance at the end of the period 892 948 1,167      
Ending Balance collectively evaluated for impairment       892 948  
Total ending allowance balance $ 948 $ 1,167 $ 699 892 948 $ 1,167
Loans            
Ending Balance individually evaluated for impairment       130 113  
Ending Balance collectively evaluated for impairment       61,775 56,658  
Total ending loan balance excluding accrued interest       61,905 $ 56,771  
Cheviot Financial Corp.            
Loans            
Purchased credit impaired loans       $ 16,175