Cover Page - shares	6 Months Ended
	Jun. 30, 2021	Jul. 30, 2021
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2021
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	145 Bank Street
Entity Address, City or Town	Waterbury
Entity Address, State or Province	CT
Entity Address, Postal Zip Code	06702
City Area Code	203
Local Phone Number	578-2202
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
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		90,592,291
Entity Central Index Key	0000801337
Current Fiscal Year End Date	--12-31
Amendment Flag	false
Document Fiscal Period Focus	Q2
Document Fiscal Year Focus	2021
Common Class A [Member]
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