LOANS AND ALLOWANCE - Aging of the Recorded Investment in Past Due Loans - (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Recorded investment in nonaccrual and loans past due over 90 days still on accrual and aging of recorded investment in past due
Non-accrual	$ 20,181	$ 15,808
Past due over 90 days and still accruing		2,135
Aging of the recorded investment in past due loans
Total ending loan balance excluding accrued interest	2,614,610	2,651,673
Total Past Due	18,878	23,234
Loans Not Past Due	2,595,732	2,628,439
Accrued interest	7,211	7,342
30-59 Days Past Due
Aging of the recorded investment in past due loans
Total Past Due	7,426	9,640
60-89 Days Past Due
Aging of the recorded investment in past due loans
Total Past Due	917	2,229
Greater Than 90 Days Past Due
Aging of the recorded investment in past due loans
Total Past Due	10,535	11,365
Cheviot Financial Corp.
Recorded investment in nonaccrual and loans past due over 90 days still on accrual and aging of recorded investment in past due
Non-accrual	7,005	3,564
Commercial
Aging of the recorded investment in past due loans
Total ending loan balance excluding accrued interest	528,166	534,559
Commercial | Commercial and industrial
Recorded investment in nonaccrual and loans past due over 90 days still on accrual and aging of recorded investment in past due
Non-accrual	431	882
Aging of the recorded investment in past due loans
Total ending loan balance excluding accrued interest	458,019	461,092
Total Past Due	134	176
Loans Not Past Due	457,885	460,916
Commercial | Commercial and industrial | 30-59 Days Past Due
Aging of the recorded investment in past due loans
Total Past Due	21
Commercial | Commercial and industrial | 60-89 Days Past Due
Aging of the recorded investment in past due loans
Total Past Due	10
Commercial | Commercial and industrial | Greater Than 90 Days Past Due
Aging of the recorded investment in past due loans
Total Past Due	103	176
Commercial | Agricultural
Recorded investment in nonaccrual and loans past due over 90 days still on accrual and aging of recorded investment in past due
Non-accrual	1,805	1,631
Aging of the recorded investment in past due loans
Total ending loan balance excluding accrued interest	70,147	73,467
Total Past Due	1,781	1,821
Loans Not Past Due	68,366	71,646
Commercial | Agricultural | 30-59 Days Past Due
Aging of the recorded investment in past due loans
Total Past Due	130	215
Commercial | Agricultural | 60-89 Days Past Due
Aging of the recorded investment in past due loans
Total Past Due	39
Commercial | Agricultural | Greater Than 90 Days Past Due
Aging of the recorded investment in past due loans
Total Past Due	1,612	1,606
Commercial Real Estate
Aging of the recorded investment in past due loans
Total ending loan balance excluding accrued interest	1,143,213	1,162,696
Commercial Real Estate | Farm
Recorded investment in nonaccrual and loans past due over 90 days still on accrual and aging of recorded investment in past due
Non-accrual	1,691	1,347
Aging of the recorded investment in past due loans
Total ending loan balance excluding accrued interest	108,037	111,807
Total Past Due	1,570	1,324
Loans Not Past Due	106,467	110,483
Commercial Real Estate | Farm | 30-59 Days Past Due
Aging of the recorded investment in past due loans
Total Past Due	2	81
Commercial Real Estate | Farm | Greater Than 90 Days Past Due
Aging of the recorded investment in past due loans
Total Past Due	1,568	1,243
Commercial Real Estate | Hotel
Recorded investment in nonaccrual and loans past due over 90 days still on accrual and aging of recorded investment in past due
Non-accrual	2,983	64
Aging of the recorded investment in past due loans
Total ending loan balance excluding accrued interest	101,685	91,213
Total Past Due		63
Loans Not Past Due	101,685	91,150
Commercial Real Estate | Hotel | Greater Than 90 Days Past Due
Aging of the recorded investment in past due loans
Total Past Due		63
Commercial Real Estate | Construction and development
Recorded investment in nonaccrual and loans past due over 90 days still on accrual and aging of recorded investment in past due
Non-accrual	1,525	122
Past due over 90 days and still accruing		2,135
Aging of the recorded investment in past due loans
Total ending loan balance excluding accrued interest	84,939	102,598
Total Past Due	1,506	3,639
Loans Not Past Due	83,433	98,959
Commercial Real Estate | Construction and development | 30-59 Days Past Due
Aging of the recorded investment in past due loans
Total Past Due		1,416
Commercial Real Estate | Construction and development | Greater Than 90 Days Past Due
Aging of the recorded investment in past due loans
Total Past Due	1,506	2,223
Commercial Real Estate | Other
Recorded investment in nonaccrual and loans past due over 90 days still on accrual and aging of recorded investment in past due
Non-accrual	3,015	3,219
Aging of the recorded investment in past due loans
Total ending loan balance excluding accrued interest	848,552	857,078
Total Past Due	3,384	3,170
Loans Not Past Due	845,168	853,908
Commercial Real Estate | Other | 30-59 Days Past Due
Aging of the recorded investment in past due loans
Total Past Due	1,967	1,268
Commercial Real Estate | Other | 60-89 Days Past Due
Aging of the recorded investment in past due loans
Total Past Due	188	90
Commercial Real Estate | Other | Greater Than 90 Days Past Due
Aging of the recorded investment in past due loans
Total Past Due	1,229	1,812
Residential
Aging of the recorded investment in past due loans
Total ending loan balance excluding accrued interest	880,803	892,513
Residential | 1-4 family
Recorded investment in nonaccrual and loans past due over 90 days still on accrual and aging of recorded investment in past due
Non-accrual	6,399	7,163
Aging of the recorded investment in past due loans
Total ending loan balance excluding accrued interest	601,338	608,366
Total Past Due	8,138	10,148
Loans Not Past Due	593,200	598,218
Residential | 1-4 family | 30-59 Days Past Due
Aging of the recorded investment in past due loans
Total Past Due	4,874	4,884
Residential | 1-4 family | 60-89 Days Past Due
Aging of the recorded investment in past due loans
Total Past Due	636	2,002
Residential | 1-4 family | Greater Than 90 Days Past Due
Aging of the recorded investment in past due loans
Total Past Due	2,628	3,262
Residential | Home equity
Recorded investment in nonaccrual and loans past due over 90 days still on accrual and aging of recorded investment in past due
Non-accrual	1,323	1,273
Aging of the recorded investment in past due loans
Total ending loan balance excluding accrued interest	279,465	284,147
Total Past Due	1,349	1,881
Loans Not Past Due	278,116	282,266
Residential | Home equity | 30-59 Days Past Due
Aging of the recorded investment in past due loans
Total Past Due	394	830
Residential | Home equity | 60-89 Days Past Due
Aging of the recorded investment in past due loans
Total Past Due	44	137
Residential | Home equity | Greater Than 90 Days Past Due
Aging of the recorded investment in past due loans
Total Past Due	911	914
Consumer
Aging of the recorded investment in past due loans
Total ending loan balance excluding accrued interest	62,428	61,905
Consumer | Direct
Recorded investment in nonaccrual and loans past due over 90 days still on accrual and aging of recorded investment in past due
Non-accrual	1,009	107
Aging of the recorded investment in past due loans
Total ending loan balance excluding accrued interest	62,132	61,574
Total Past Due	1,016	1,002
Loans Not Past Due	61,116	60,572
Consumer | Direct | 30-59 Days Past Due
Aging of the recorded investment in past due loans
Total Past Due	38	936
Consumer | Direct | Greater Than 90 Days Past Due
Aging of the recorded investment in past due loans
Total Past Due	978	66
Consumer | Indirect
Aging of the recorded investment in past due loans
Total ending loan balance excluding accrued interest	296	331
Total Past Due		10
Loans Not Past Due	$ 296	321
Consumer | Indirect | 30-59 Days Past Due
Aging of the recorded investment in past due loans
Total Past Due		$ 10