v3.26.1
Document and Entity Information - shares
 6 Months Ended
Jun. 30, 2026
Aug. 13, 2026
Cover [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Transition Report false  
Document Period End Date Jun. 30, 2026  
Entity Central Index Key 0002058758  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2026  
Document Fiscal Period Focus Q2  
Amendment Flag false  
Entity File Number 001-42775  
Entity Registrant Name Avidia Bancorp, Inc.  
Entity Incorporation, State or Country Code MD  
Entity Tax Identification Number 33-4239888  
Entity Address, Address Line One 42 Main Street  
Entity Address, City or Town Hudson  
Entity Address, State or Province MA  
Entity Address, Postal Zip Code 01749  
City Area Code 800  
Local Phone Number 508-2265  
Title of 12(b) Security Common stock, $0.01 par value  
Trading Symbol AVBC  
Security Exchange Name NYSE  
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   19,970,306