Retirement Benefit Plans (Weighted Average Assumptions used to Determine Benefit Obligations) (Details)	Dec. 31, 2015	Dec. 31, 2014
Webster Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate (as a percent)	4.20%	3.85%
Webster SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate (as a percent)	3.75%	3.50%
Postretirement Health Coverage [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate (as a percent)	3.35%	3.15%