LOANS AND ALLOWANCE FOR LOAN LOSSES - Allowance for Loan Losses and Recorded Investment By Portfolio Segment - (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015	Sep. 30, 2016	Dec. 31, 2015
Allowance for loan losses
Balance at the beginning of the period	$ 21,468	$ 22,473	$ 22,020	$ 23,250	$ 23,250
Provision charged to expense	150	800	855	800
Losses charged off	(1,209)	(2,351)	(4,979)	(5,620)
Recoveries	1,419	1,101	3,932	3,593
Balance at the end of the period	21,828	22,023	21,828	22,023	22,020
Loans
Ending Balance individually evaluated for impairment						$ 1,252	$ 1,429
Ending Balance collectively evaluated for impairment						20,576	20,591
Total ending allowance balance	21,468	22,473	22,020	23,250	23,250	21,828	22,020
Loans
Ending Balance individually evaluated for impairment						20,412	18,989
Ending Balance collectively evaluated for impairment						2,564,495	2,136,403
Total ending loan balance excluding accrued interest						2,584,907	2,155,392
Accrued interest						6,911	5,878
Allowance that includes a probability of default for subject loans			2,410		1,583
Commercial
Allowance for loan losses
Balance at the beginning of the period	6,940	5,394	6,511	2,977	2,977
Provision charged to expense	1,525	1,331	2,352	3,822
Losses charged off	(23)	(773)	(650)	(900)
Recoveries	148	246	377	299
Balance at the end of the period	8,590	6,198	8,590	6,198	6,511
Loans
Ending Balance individually evaluated for impairment						454	92
Ending Balance collectively evaluated for impairment						8,136	6,419
Total ending allowance balance	6,940	5,394	6,511	2,977	2,977	8,590	6,511
Loans
Ending Balance individually evaluated for impairment						2,329	812
Ending Balance collectively evaluated for impairment						488,030	444,852
Total ending loan balance excluding accrued interest						490,359	445,664
Commercial Real Estate
Allowance for loan losses
Balance at the beginning of the period	8,780	12,689	10,702	15,605	15,605
Provision charged to expense	(1,225)	(1,349)	(3,314)	(5,298)
Losses charged off	(33)	(101)	(614)	(538)
Recoveries	398	307	1,146	1,777
Balance at the end of the period	7,920	11,546	7,920	11,546	10,702
Loans
Ending Balance individually evaluated for impairment						650	1,166
Ending Balance collectively evaluated for impairment						7,270	9,536
Total ending allowance balance	8,780	12,689	10,702	15,605	15,605	7,920	10,702
Loans
Ending Balance individually evaluated for impairment						7,870	8,909
Ending Balance collectively evaluated for impairment						1,118,126	916,975
Total ending loan balance excluding accrued interest						1,125,996	925,884
Residential
Allowance for loan losses
Balance at the beginning of the period	4,677	3,264	3,859	3,501	3,501
Provision charged to expense	(257)	154	1,214	927
Losses charged off	(122)	(401)	(967)	(1,606)
Recoveries	106	71	298	266
Balance at the end of the period	4,404	3,088	4,404	3,088	3,859
Loans
Ending Balance individually evaluated for impairment						148	171
Ending Balance collectively evaluated for impairment						4,256	3,688
Total ending allowance balance	4,677	3,264	3,859	3,501	3,501	4,404	3,859
Loans
Ending Balance individually evaluated for impairment						10,092	9,155
Ending Balance collectively evaluated for impairment						897,433	717,918
Total ending loan balance excluding accrued interest						907,525	727,073
Consumer
Allowance for loan losses
Balance at the beginning of the period	1,071	1,126	948	1,167	1,167
Provision charged to expense	107	664	603	1,349
Losses charged off	(1,031)	(1,076)	(2,748)	(2,576)
Recoveries	767	477	2,111	1,251
Balance at the end of the period	914	1,191	914	1,191	948
Loans
Ending Balance collectively evaluated for impairment						914	948
Total ending allowance balance	$ 1,071	$ 1,126	$ 948	$ 1,167	$ 1,167	914	948
Loans
Ending Balance individually evaluated for impairment						121	113
Ending Balance collectively evaluated for impairment						60,906	56,658
Total ending loan balance excluding accrued interest						61,027	$ 56,771
Cheviot Financial Corp.
Loans
Purchased credit impaired loans						16,175
Non accretable yield						4,615
Accretable yield						0
Allowance for loan losses on loans acquired in transfer						$ 0