Defined Benefit Plan, Employer Discretionary Contribution Amount

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- Definition

Share-based Compensation Arrangement By Share-based Payment Award, Reduction Of Shares Available To Be Issued Upon Exercise Of Stock Options With Each Additional Restricted Stock Grant

+ References

No definition available.

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- Definition

The total amount of cash and securities held by third party trustees pursuant to terms of debt instruments or other agreements as of the date of each statement of financial position presented, which can be used by the trustee only to pay the noncurrent portion of specified obligations.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(b))
-URI https://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

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- Definition

Amount of cost to be recognized for nonvested award under share-based payment arrangement. Excludes share and unit options.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

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- Definition

Amount of tax benefit for recognition of expense of award under share-based payment arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

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- Definition

Amount of noncash expense for share-based payment arrangement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
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- Definition

Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

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- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(01)
-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(02)
-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

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- Definition

Number of shares authorized for issuance under share-based payment arrangement.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(3)
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- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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- Definition

Gross number of share options (or share units) granted during the period.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(01)
-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

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- Definition

Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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-SubTopic 10
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Employee Benefits - Narrative (Details) - USD ($)				1 Months Ended	3 Months Ended		9 Months Ended		10 Months Ended	12 Months Ended
Employee Benefits - Narrative (Details) - USD ($)	May 17, 2022	Mar. 01, 2022	Nov. 29, 2021	Dec. 31, 2021	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Dec. 31, 2021
Defined Benefit Plan, Plan Assets, Category [Line Items]
Share-based compensation arrangement by share-based payment award, reduction of shares available to be issued upon exercise of stock options with each additional restricted stock grant			3
Share-based payment arrangement, noncash expense							$ 8,092,000	$ 0
Restricted Stock Units (RSUs)
Defined Benefit Plan, Plan Assets, Category [Line Items]
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period (in shares)		978,364					978,364
Restricted Stock
Defined Benefit Plan, Plan Assets, Category [Line Items]
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period (in shares)	31,559						31,559
Performance Shares
Defined Benefit Plan, Plan Assets, Category [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting period		3 years
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period (in shares)		533,676					533,676
Eastern Bankshares, Inc. 2021 Equity Incentive Plan
Defined Benefit Plan, Plan Assets, Category [Line Items]
Share-based compensation arrangement by share-based payment award, number of shares authorized (in shares)			26,146,141
Share-based payment arrangement, noncash expense					$ 3,600,000	$ 0	$ 8,100,000	0
Share-based payment arrangement, expense, tax benefit					1,000,000		2,300,000
Share-based payment arrangement, nonvested award, excluding option, cost not yet recognized, amount				$ 13,500,000	$ 40,800,000		$ 40,800,000		$ 40,800,000	$ 13,500,000
Share-based payment arrangement, nonvested award, cost not yet recognized, period for recognition							3 years 7 months 6 days			4 years 10 months 24 days
Eastern Bankshares, Inc. 2021 Equity Incentive Plan \| Restricted Stock Units (RSUs)
Defined Benefit Plan, Plan Assets, Category [Line Items]
Share-based compensation arrangement by share-based payment award, number of shares authorized (in shares)			7,470,326
Share-based compensation arrangement by share-based payment award, number of shares available for grant (in shares)				6,787,270	5,243,671		5,243,671		5,243,671	6,787,270
Share-based compensation arrangement by share-based payment award, equity instruments other than options, vested in period (in shares)				0					0
Eastern Bankshares, Inc. 2021 Equity Incentive Plan \| Restricted Stock Units (RSUs) \| Minimum
Defined Benefit Plan, Plan Assets, Category [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting period		3 years
Eastern Bankshares, Inc. 2021 Equity Incentive Plan \| Restricted Stock Units (RSUs) \| Maximum
Defined Benefit Plan, Plan Assets, Category [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting period		5 years
Eastern Bankshares, Inc. 2021 Equity Incentive Plan \| Share-based Payment Arrangement, Option
Defined Benefit Plan, Plan Assets, Category [Line Items]
Share-based compensation arrangement by share-based payment award, number of shares authorized (in shares)			18,675,815
Share-based compensation arrangement by share-based payment award, expiration period			10 years
Share-based compensation arrangement by share-based payment award, number of shares available for grant (in shares)				18,675,815	18,675,815		18,675,815		18,675,815	18,675,815
Share-based compensation arrangement by share-based payment award, options, grants in period, gross (in shares)				0					0
Eastern Bankshares, Inc. 2021 Equity Incentive Plan \| Restricted Stock
Defined Benefit Plan, Plan Assets, Category [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting period	1 year		5 years
Primary Beneficiary
Defined Benefit Plan, Plan Assets, Category [Line Items]
Rabbi trust investments				$ 104,372,000	$ 71,650,000		$ 71,650,000		$ 71,650,000	$ 104,372,000
Pension Plan
Defined Benefit Plan, Plan Assets, Category [Line Items]
Discretionary employer contributions to defined benefit plans						$ 0	$ 7,200,000	$ 0