v3.26.1
Document and Entity Information - shares
 3 Months Ended
Mar. 31, 2026
Jun. 29, 2026
Document and Entity Information [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Mar. 31, 2026  
Document Transition Report false  
Entity File Number 333-294289  
Entity Registrant Name CSB Financial Inc.  
Entity Incorporation, State or Country Code MD  
Entity Tax Identification Number 41-4994538  
Entity Address, Address Line One 503 West Plane Street,  
Entity Address, City or Town Bethel  
Entity Address State Or Province OH  
Entity Address, Postal Zip Code 45106  
City Area Code 513  
Local Phone Number 734-4445  
Entity Current Reporting Status No  
Entity Interactive Data Current Yes  
Entity Filer Category Non-accelerated Filer  
Entity Small Business true  
Entity Emerging Growth Company true  
Entity Ex Transition Period false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   0
Entity Central Index Key 0002114521  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2026  
Document Fiscal Period Focus Q1  
Amendment Flag false