CAPITAL (Tables)

12 Months Ended

Dec. 31, 2023

Banking Regulation, Total Capital [Abstract]

Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table Text Block]

	Actual				Minimum capital required - Basel III				PCA requirement to be considered well capitalized
(Dollars in thousands)	Capital amount		Ratio		Capital amount		Ratio		Capital amount		Ratio
December 31, 2023
Common equity tier 1 capital to risk-weighted assets
Consolidated	$	1,568,815	11.73	%	$	936,192	7.00	%	N/A		N/A
First Financial Bank	1,701,338		12.73	%	935,746		7.00	%	$	868,907	6.50	%
Tier 1 capital to risk-weighted assets
Consolidated	1,613,480		12.06	%	1,136,805		8.50	%	N/A		N/A
First Financial Bank	1,701,840		12.73	%	1,136,263		8.50	%	1,069,424		8.00	%
Total capital to risk-weighted assets
Consolidated	1,820,285		13.61	%	1,404,289		10.50	%	N/A		N/A
First Financial Bank	1,743,521		13.04	%	1,403,619		10.50	%	1,336,780		10.00	%
Leverage
Consolidated	1,613,480		9.70	%	665,125		4.00	%	N/A		N/A
First Financial Bank	1,701,840		10.24	%	664,781		4.00	%	830,976		5.00	%

	Actual				Minimum capital required - Basel III				PCA requirement to be considered well capitalized
(Dollars in thousands)	Capital amount		Ratio		Capital amount		Ratio		Capital amount		Ratio
December 31, 2022
Common equity tier 1 capital to risk-weighted assets
Consolidated	$	1,399,420	10.83	%	$	904,626	7.00	%	N/A		N/A
First Financial Bank	1,581,328		12.26	%	903,244		7.00	%	$	838,726	6.50	%
Tier 1 capital to risk-weighted assets
Consolidated	1,443,698		11.17	%	1,098,475		8.50	%	N/A		N/A
First Financial Bank	1,581,900		12.26	%	1,096,796		8.50	%	1,032,278		8.00	%
Total capital to risk-weighted assets
Consolidated	1,691,255		13.09	%	1,356,939		10.50	%	N/A		N/A
First Financial Bank	1,640,671		12.71	%	1,354,865		10.50	%	1,290,348		10.00	%
Leverage
Consolidated	1,443,698		8.89	%	649,636		4.00	%	N/A		N/A
First Financial Bank	1,581,900		9.76	%	648,607		4.00	%	810,759		5.00	%