Acquisition (Estimated Fair Values of Assets and Liabilities) (Details) - USD ($) $ in Thousands			12 Months Ended
		Jan. 13, 2015	Dec. 31, 2015
Business Combinations [Abstract]
Cash		$ 1,446,898
Intangible assets		43,000
Total identifiable assets acquired		1,489,898
Deposits		1,446,899
Contingent liability	[1]	6,000
Total liabilities assumed		1,452,899
Net identifiable assets acquired		36,999
Goodwill		8,486	$ 8,486
Net assets acquired		$ 45,485

[1] The contingent liability represents an obligation that existed at the acquisition date. Accordingly, Webster assumed the contingent liability as part of the transaction and has accounted for it at fair value.