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Retirement Benefit Plans - Weighted Average Assumptions used to Determine Benefit Obligations (Details) | Dec. 31, 2024 | Dec. 31, 2023
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Pension | Webster Bank Pension Plan |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Discount Rate | 5.43% | 4.76%
SERP | Webster Bank Supplemental Defined Benefit Plan for Executive Officers |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Discount Rate | 5.31% | 4.68%
SERP | Astoria Bank Excess Benefit and Supplemental Benefit Plans |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Discount Rate | 5.14% | 4.56%
SERP | Astoria Bank Directors’ Retirement Plan |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Discount Rate | 5.04% | 4.50%
SERP | Retirement Plan of the Greater New York Savings Bank for Non-Employee Directors |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Discount Rate | 5.03% | 4.50%
SERP | Supplemental Executive Retirement Plan of Provident Bank |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Discount Rate | 5.32% | 4.83%
SERP | Supplemental Executive Retirement Plan of Provident Bank - Other |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Discount Rate | 5.09% | 4.71%
OPEB | Webster Bank Postretirement Medical Benefit Plan |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Discount Rate | 5.01% | 4.54%
OPEB | Sterling Bancorp Supplemental Postretirement Life Insurance Plan |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Discount Rate | 5.20% | 4.51%
OPEB | Astoria Bank Postretirement Welfare Benefit Plans |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Discount Rate | 5.39% | 4.74%
OPEB | Split Dollar Life Insurance Arrangement |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Discount Rate |  | 4.45%

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- Definition Weighted average rate for present value of future retirement benefits cash flows, used to determine benefit obligation of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (k)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 + Details
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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. + Details
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