v3.26.3
Document and Entity Information - shares
6 Months Ended
Jun. 30, 2026
Sep. 21, 2026
Cover [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Jun. 30, 2026  
Entity Central Index Key 0002138186  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2026  
Document Fiscal Period Focus Q2  
Document Quarterly Report true  
Document Transition Report false  
Entity File Number 333-296731  
Entity Registrant Name NARRAGANSETT BANCORP, INC.  
Entity Incorporation, State or Country Code MD  
Entity Tax Identification Number 42-3540071  
Entity Address, Address Line One 330 Swansea Mall Drive  
Entity Address, City or Town Swansea  
Entity Address, State or Province MA  
Entity Address, Postal Zip Code 02777  
City Area Code 888  
Local Phone Number 806-2872  
Entity Current Reporting Status Yes  
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