Retirement Benefit Plans (Changes in Other Comprehensive Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net loss (gain)	$ 5,367	$ 30,683	$ (26,949)
Amounts reclassified from accumulated other comprehensive income	(2,809)	(37)	(3,169)
Total defined benefit pension and postretirement benefit plans	2,485	30,573	(30,191)
Webster Pension [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net loss (gain)	8,525	31,951	(23,238)
Amounts reclassified from accumulated other comprehensive income	(5,724)	(2,781)	(6,355)
Amortization of prior service cost	0	0	0
Total defined benefit pension and postretirement benefit plans	2,801	29,170	(29,593)
Webster SERP [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net loss (gain)	372	1,145	(160)
Amounts reclassified from accumulated other comprehensive income	(390)	(134)	(125)
Amortization of prior service cost	0	0	0
Total defined benefit pension and postretirement benefit plans	(18)	1,011	(285)
Postretirement Health Coverage [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net loss (gain)	(178)	470	(239)
Amounts reclassified from accumulated other comprehensive income	(47)	(5)	0
Amortization of prior service cost	(73)	(73)	(73)
Total defined benefit pension and postretirement benefit plans	$ (298)	$ 392	$ (312)