Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2017	Oct. 31, 2017
Document and Entity Information [Abstract]
Document Period End Date	Sep. 30, 2017
Document Type	10-Q
Amendment Flag	false
Entity Registrant Name	WEBSTER FINANCIAL CORPORATION
Entity Common Stock, Shares Outstanding		92,074,790
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q3
Trading Symbol	WBS
Entity Central Index Key	0000801337
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer