Document And Entity Information - shares	9 Months Ended
	Sep. 30, 2019	Nov. 08, 2019
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Trading Symbol	OPBK
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
Entity Common Stock, Shares Outstanding		15,702,743
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 Quarterly Report	true
Document Transition Report	false
Entity Incorporation, State or Country Code	CA
Title of 12(b) Security	Common Stock, no par value
Security Exchange Name	NASDAQ
Entity Interactive Data Current	Yes