Cover - USD ($)	12 Months Ended
	Dec. 31, 2025	Mar. 11, 2026	Jun. 30, 2025
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Annual Report	true
Document Transition Report	false
Document Period End Date	Dec. 31, 2025
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2025
Current Fiscal Year End Date	--12-31
Entity File Number	0-16540
Entity Registrant Name	UNITED BANCORP, INC.
Entity Central Index Key	0000731653
Entity Tax Identification Number	34-1405357
Entity Incorporation, State or Country Code	OH
Entity Address, Address Line One	201 South Fourth Street
Entity Address, City or Town	Martins Ferry
Entity Address, State or Province	OH
Entity Address, Postal Zip Code	43935
City Area Code	(740)
Local Phone Number	633-0445
Title of 12(b) Security	Common Stock, Par Value $1.00
Trading Symbol	UBCP
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	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 66,087,390
Entity Common Stock, Shares Outstanding		5,756,852
Documents Incorporated by Reference [Text Block]	Portions of the proxy statement for the Annual Shareholders meeting to be held April 22, 2026 are incorporated by reference into Part III. Portions of the Annual Report to Shareholders for the year ended December 31, 2025 are incorporated by reference into Parts I and II.
ICFR Auditor Attestation Flag	false
Document Financial Statement Error Correction [Flag]	false
Auditor Name	S. R. Snodgrass, P.C.
Auditor Location	Cranberry, PA
Auditor Firm ID	74