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