Cover - USD ($) $ in Billions	12 Months Ended
Cover - USD ($) $ in Billions	Dec. 31, 2025	Apr. 13, 2026	Jun. 30, 2025
Entity Information [Line Items]
Document Type	10-K/A
Document Annual Report	true
Current Fiscal Year End Date	--12-31
Document Period End Date	Dec. 31, 2025
Document Transition Report	false
Entity File Number	001-31486
Entity Registrant Name	WEBSTER FINANCIAL CORPORATION
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	06-1187536
Entity Address, Address Line One	200 Elm Street
Entity Address, City or Town	Stamford
Entity Address, State or Province	CT
Entity Address, Postal Zip Code	06902
City Area Code	203
Local Phone Number	578-2202
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity Public Float			$ 9.1
Entity Common Stock, Shares Outstanding		162,031,299
Documents Incorporated by Reference	None.
Amendment Flag	true
Entity Central Index Key	0000801337
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2025
Amendment Description	Webster Financial Corporation (the “Company”) is filing this Amendment No. 1 on Form 10-K/A (this “Amendment”) to amend its 2025 Annual Report on Form 10-K filed with the Securities and Exchange Commission (the “SEC”) on February 27, 2026 (the “Form 10-K”). This Amendment is being filed for the purpose of including the information required by Items 10 through 14 of Part III of Form 10-K not included in the Form 10-K.This information required by Items 10 through 14 of Part III of Form 10-K was previously omitted from the Form 10-K in reliance on SEC general instructions to Form 10-K, which permit the information in the above referenced items to be incorporated in a Form 10-K by reference from a definitive proxy statement if such statement is filed no later than 120 days after a company’s fiscal year-end. We are filing this Amendment to include Part III information in the Form 10-K because our definitive proxy statement containing this information will not be filed before that date.As such, this Amendment hereby amends and supplements Items 10 through 14 of Part III of the Form 10-K and amends and updates the Form 10-K cover page (primarily to update the number of shares of Common Stock outstanding to April 13, 2026). In addition, in accordance with applicable SEC rules, Item 15 of Part IV of the Form 10-K has been supplemented to include currently dated certifications pursuant to Section 302 of the Sarbanes-Oxley Act of 2002. The cover page of the Form 10-K is also amended to delete the reference to incorporation by reference of this Amendment.Except as described above, this Amendment does not amend, update or change any other items or disclosures in the Form 10-K and does not purport to reflect any information or events subsequent to the filing of the Form 10-K. As such, this Amendment speaks only as of the date the Form 10-K was filed, and we have not undertaken herein to amend, supplement or update any information contained in the Form 10-K to give effect to any subsequent events. Accordingly, this Amendment should be read in conjunction with our Form 10-K and with our filings with the SEC subsequent to the filing of our Form 10-K.The Company expected to hold its 2026 Annual Meeting of Stockholders in May 2026. On February 3, 2026, the Company entered into a Transaction Agreement (the “Transaction Agreement”) with Banco Santander, S.A., a Spanish sociedad anónima (“Banco Santander”), and Webster Virginia Corporation, a wholly owned subsidiary of Webster incorporated in the State of Virginia. The Transaction Agreement provides that, upon the terms and subject to the conditions set forth therein, Banco Santander will acquire Webster in two steps (the "Transaction"). Due to the fact that the Company now expects to hold a Special Meeting of Stockholders in the second quarter of 2026, and the Company and Banco Santander expect the Transaction to close in the second half of 2026, subject to customary conditions, including the receipt of Webster stockholder approval and required regulatory approvals, the Board of Directors has decided a 2026 Annual Meeting will not be held at this time while the Transaction is pending. In the event the Company decides to hold a 2026 Annual Meeting, a press release will be issued, with sufficient notice to stockholders, announcing: (i) the date, time and location of the 2026 Annual Meeting; and (ii) the new deadline for receipt of stockholder proposals submitted pursuant to Rule 14a-8 under the Securities Exchange Act of 1934 for inclusion in the Company’s proxy materials for a 2026 Annual Meeting.As used in this Amendment, the terms the “Company,” “we,” “our” and “us” refer to Webster Financial Corporation and “Webster Bank” refers to Webster Bank, N.A., a wholly-owned subsidiary of the Company. Other terms used but not defined herein are as defined in the Form 10-K.KPMG LLP (“KPMG”) issued reports on the consolidated financial statements of the Company, and the effectiveness of the Company's internal control over financial reporting, within the Form 10-K. As this Amendment speaks to the date of the Form 10-K, KPMG’s reports speak only as to February 27, 2026. We have made no substantive changes to the Form 10-K other than those noted above.
Common Class A
Entity Information [Line Items]
Title of 12(b) Security	Common Stock, par value $0.01 per share
Trading Symbol	WBS
Security Exchange Name	NYSE
Series F Preferred Stock [Member]
Entity Information [Line Items]
Title of 12(b) Security	Depositary Shares, each representing 1/1000th interest in a share
Trading Symbol	WBS-PrF
Security Exchange Name	NYSE
Series G Preferred Stock [Member]
Entity Information [Line Items]
Title of 12(b) Security	Depositary Shares, each representing 1/40th interest in a share
Trading Symbol	WBS-PrG
Security Exchange Name	NYSE

WEBSTER FINANCIAL CORP 10-K/A