Retirement Benefit Plans (Summary of Components of Accumulated Other Comprehensive Loss Related to Pensions and Postretirement Benefits) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Deferred tax benefit	$ 918	$ 11,147	$ (10,812)
Webster Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	73,238	70,437
Prior service cost	0	0
Total pre-tax amounts included in accumulated other comprehensive loss	73,238	70,437
Deferred tax benefit	26,447	25,415
Amounts included in accumulated other comprehensive loss, net of tax	46,791	45,022
Webster SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	2,412	2,430
Prior service cost	0	0
Total pre-tax amounts included in accumulated other comprehensive loss	2,412	2,430
Deferred tax benefit	871	877
Amounts included in accumulated other comprehensive loss, net of tax	1,541	1,553
Postretirement Health Coverage [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	591	816
Prior service cost	14	87
Total pre-tax amounts included in accumulated other comprehensive loss	605	903
Deferred tax benefit	218	326
Amounts included in accumulated other comprehensive loss, net of tax	$ 387	$ 577