v3.26.1
Employee Benefits - Share-Based Payment Arrangement, Activity (Details) - shares
1 Months Ended 6 Months Ended
Nov. 29, 2021
May 31, 2026
Mar. 31, 2026
May 31, 2025
Mar. 31, 2025
Jun. 30, 2026
Jun. 30, 2025
RSU              
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]              
Shares granted (in shares)           445,254 630,493
RSU | Eastern Bankshares, Inc. 2021 Equity Incentive Plan              
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]              
Shares granted (in shares)     445,254   630,493    
Vesting Period (Approximate from date of grant)     3 years   3 years    
PSU              
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]              
Shares granted (in shares)           208,358 339,503
PSU | Eastern Bankshares, Inc. 2021 Equity Incentive Plan              
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]              
Shares granted (in shares)     208,358   339,503    
Vesting Period (Approximate from date of grant)     2 years 9 months 18 days   2 years 9 months 18 days    
RSA              
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]              
Shares granted (in shares)           58,245 54,236
RSA | Eastern Bankshares, Inc. 2021 Equity Incentive Plan              
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]              
Shares granted (in shares)   58,245   54,236      
Vesting Period (Approximate from date of grant) 5 years 1 year   1 year