Retirement Benefit Plans (Changes in Plan Assets and Funded Status of Pension Plans and Other Postretirement Benefit Plans) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Change in plan assets:
Beginning balance	$ 172,976
Ending balance	161,369	$ 172,976
Webster Pension [Member]
Change in benefit obligation:
Beginning balance	210,548	171,189
Service cost	45	40	$ 40
Interest cost	8,008	8,068	7,365
Actuarial (gain) loss	(8,588)	38,472
Benefit payments, administrative expenses, and interest income, net	(6,368)	(7,221)
Ending balance	203,645	210,548	171,189
Change in plan assets:
Beginning balance	172,976	162,182
Actual return on plan assets	(5,239)	18,015
Employer contributions	0	0
Benefits paid and administrative expenses	(6,368)	(7,221)
Ending balance	161,369	172,976	162,182
Funded status of the plan at year end	(42,276)	(37,572)
Webster SERP [Member]
Change in benefit obligation:
Beginning balance	10,041	8,675
Service cost	0	0	0
Interest cost	345	364	289
Actuarial (gain) loss	373	1,145
Benefit payments, administrative expenses, and interest income, net	(241)	(143)
Ending balance	10,518	10,041	8,675
Change in plan assets:
Beginning balance	0	0
Actual return on plan assets	0	0
Employer contributions	241	143
Benefits paid and administrative expenses	(241)	(143)
Ending balance	0	0	0
Funded status of the plan at year end	(10,518)	(10,041)
Postretirement Health Coverage [Member]
Change in benefit obligation:
Beginning balance	4,133	3,821
Service cost	0	0	0
Interest cost	123	139	109
Actuarial (gain) loss	(178)	470
Benefit payments, administrative expenses, and interest income, net	(225)	(297)
Ending balance	3,853	4,133	3,821
Change in plan assets:
Beginning balance	0	0
Actual return on plan assets	0	0
Employer contributions	225	297
Benefits paid and administrative expenses	(225)	(297)
Ending balance	0	0	$ 0
Funded status of the plan at year end	$ (3,853)	$ (4,133)