v3.26.1
Employee Benefits - Share-Based Payment Arrangement, Activity (Details) - shares
1 Months Ended 3 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2026
Mar. 31, 2025
Restricted Stock Units (RSUs)        
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]        
Grants in period (in shares)     445,254 630,493
Restricted Stock Units (RSUs) | Eastern Bankshares, Inc. 2021 Equity Incentive Plan        
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]        
Grants in period (in shares) 445,254 630,493    
Award vesting period 3 years 3 years    
Performance Shares        
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]        
Grants in period (in shares)     208,358 339,503
Performance Shares | Eastern Bankshares, Inc. 2021 Equity Incentive Plan        
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]        
Grants in period (in shares) 208,358 339,503    
Award vesting period 2 years 9 months 18 days 2 years 9 months 18 days