Retirement Benefit Plans (Weighted Average Assumptions used to Determine Net Periodic Benefit Cost) (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Assumed healthcare cost trend (as a percent)	8.00%
Webster Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate (as a percent)	3.85%	4.80%	3.90%
Expected long-term return on assets (as a percent)	7.00%	7.25%	7.50%
Webster SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate (as a percent)	3.50%	4.25%	3.40%
Postretirement Health Coverage [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate (as a percent)	3.15%	3.75%	2.85%
Assumed healthcare cost trend (as a percent)	8.00%	8.00%	8.00%