SHARE-BASED COMPENSATION PLANS - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2024	Dec. 31, 2023
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares reserved to be issued (in shares)	1,045,000
Number of shares available to be issued under employee stock purchase plan (in shares)	665,000
Unrecognized compensation expense, recognition period	2 years 2 months 12 days
Orrstown 2011 Incentive Stock Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares reserved to be issued (in shares)	1,281,920
Number of shares available to be issued under employee stock purchase plan (in shares)	283,033
Orrstown 2011 Incentive Stock Plan \| Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense	$ 6.1	$ 3.4
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares reserved to be issued (in shares)	350,000
Number of shares available to be issued under employee stock purchase plan (in shares)	135,296
Maximum shares that can be purchased, as percentage of annual salary	10.00%
Percentage of value of the shares on the semi-annual offering	95.00%

Aggregate number of common shares reserved for future issuance.

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