Cover - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Feb. 28, 2020	Jun. 30, 2019
Cover page.
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity File Number	001-34292
Entity Registrant Name	ORRSTOWN FINANCIAL SERVICES, INC.
Entity Incorporation, State or Country Code	PA
Entity Tax Identification Number	23-2530374
Entity Address, Address Line One	77 East King Street
Entity Address, Address Line Two	P. O. Box 250
Entity Address, City or Town	Shippensburg
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	17257
City Area Code	(717)
Local Phone Number	532-6114
Title of 12(b) Security	Common Stock, no par value
Trading Symbol	ORRF
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 238.3
Entity Common Stock, Shares Outstanding (in shares)		11,256,603
Documents Incorporated by Reference	Portions of the Proxy Statement for the 2020 Annual Meeting of Shareholders are incorporated by reference in Part III of this Form 10-K.
Entity Central Index Key	0000826154
Document Fiscal Period Focus	FY
Amendment Flag	false
Document Fiscal Year Focus	2019
Current Fiscal Year End Date	--12-31