Document And Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2020	Mar. 10, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Entity Registrant Name	OP BANCORP
Entity Central Index Key	0001722010
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
ICFR Auditor Attestation Flag	false
Entity Common Stock, Shares Outstanding		15,027,635
Entity Public Float			$ 81,626,738
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity File Number	001-38437
Entity Tax Identification Number	81-3114676
Entity Address, Address Line One	1000 Wilshire Blvd
Entity Address, Address Line Two	Suite 500
Entity Address, City or Town	Los Angeles
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	90017
City Area Code	213
Local Phone Number	892-9999
Document Annual Report	true
Document Transition Report	false
Entity Incorporation, State or Country Code	CA
Title of 12(b) Security	Common Stock, no par value
Trading Symbol	OPBK
Security Exchange Name	NASDAQ
Entity Interactive Data Current	Yes
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No