REGULATORY MATTERS: (Tables)

12 Months Ended

Dec. 31, 2017

Banking and Thrift [Abstract]

Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations

The following table presents the actual and required capital amounts and related ratios for the Corporation and First Financial Bank, N.A., at year-end 2017 and 2016. 

									To Be Well Capitalized
					For Capital				Under Prompt Corrective
	Actual				Adequacy Purposes				Action Provisions
(Dollar amounts in thousands)	Amount		Ratio		Amount		Ratio		Amount	Ratio
Total risk-based capital
Corporation – 2017	$	412,525	17.88	%	$	213,446	9.250	%	N/A	N/A
Corporation – 2016	$	411,713	18.26	%	$	194,435	8.625	%	N/A	N/A
First Financial Bank – 2017	386,593		17.30	%	206,745		9.250	%	223,508	10.00	%
First Financial Bank – 2016	384,522		17.64	%	188,003		8.625	%	217,974	10.00	%
Common equity tier I capital
Corporation – 2017	$	392,615	17.01	%	$	132,682	5.750	%	N/A	N/A
Corporation – 2016	$	392,939	17.43	%	$	115,534	5.125	%	N/A	N/A
First Financial Bank – 2017	370,061		16.56	%	128,517		5.750	%	145,280	6.50	%
First Financial Bank – 2016	368,797		16.92	%	111,712		5.125	%	141,683	6.50	%
Tier I risk-based capital
Corporation – 2017	$	392,615	17.01	%	$	167,295	7.250	%	N/A	N/A
Corporation – 2016	$	392,939	17.43	%	$	149,348	6.625	%	N/A	N/A
First Financial Bank – 2017	370,061		16.56	%	162,044		7.250	%	178,807	8.00	%
First Financial Bank – 2016	368,797		16.92	%	144,408		6.625	%	174,379	8.00	%
Tier I leverage capital
Corporation – 2017	$	392,615	13.31	%	$	117,956	4.00	%	N/A	N/A
Corporation – 2016	$	392,939	13.39	%	$	117,376	4.00	%	N/A	N/A
First Financial Bank – 2017	370,061		12.81	%	115,553		4.00	%	144,441	5.00	%
First Financial Bank – 2016	368,797		12.82	%	115,047		4.00	%	143,809	5.00	%