Business Combinations (Additional Information) (Details)		4 Months Ended
	May 18, 2018 USD ($) office	Sep. 30, 2018 USD ($) office	Dec. 31, 2017 USD ($)
Business Acquisition [Line Items]
Number of branch locations acquired | office		58
Goodwill		$ 60,913,000	$ 54,058,000
First Financial Bancorp
Business Acquisition [Line Items]
Deposits acquired	$ 175,300,000
Loans acquired	117,604,000
Premium paid on deposits	$ 7,400,000
Period adjustment of premium for increase or decrease in deposits following closing date	6 months
Period adjustment for consideration transferred following closing date	6 months
Adjustment to premium paid for deposits		$ 0
Direct acquisition costs	$ 632,000
Goodwill	6,855,000
Amount of goodwill deductible for tax purposes	6,900,000
First Financial Bancorp | Core deposits
Business Acquisition [Line Items]
Intangible assets acquired	$ 3,500,000
Weighted average useful life of acquired intangibles	8 years
First Financial Bancorp | INDIANA
Business Acquisition [Line Items]
Number of branch locations acquired | office	5
First Financial Bancorp | Columbus, Indiana
Business Acquisition [Line Items]
Number of branch locations acquired | office	4
First Financial Bancorp | Greensburg, Indiana
Business Acquisition [Line Items]
Number of branch locations acquired | office	1