Employee Benefits - Schedule of Share-based Compensation Expense Under the 2021 Plan and the Related Tax Benefit (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Share-based compensation expense			$ 7,831	$ 7,712
Eastern Bankshares, Inc. 2021 Equity Incentive Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Share-based compensation expense	$ 4,200	$ 4,700	7,800	7,700
Related tax benefit	$ 1,200	$ 1,300	$ 2,200	$ 2,200