Derivative Financial Instruments (Interest Rate Swaps And Caps Not Designated For Hedge Accounting) (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012 Derivative	Dec. 31, 2011 Derivative
Customer Position Commercial Loan Interest Rate Swaps [Member]
Derivative [Line Items]
Non-designated Hedges,# of Instruments	157	127
Non-designated Hedges, Notional Amount	$ 883,617	$ 615,773
Non-designated Hedges, Estimated Fair Value	54,383	45,140
Customer Position Commercial Loan Interest Rate Swaps With Floors [Member]
Derivative [Line Items]
Non-designated Hedges,# of Instruments	11	12
Non-designated Hedges, Notional Amount	23,396	25,217
Non-designated Hedges, Estimated Fair Value	2,102	1,994
Customer Position Commercial Loan Interest Rate Caps [Member]
Derivative [Line Items]
Non-designated Hedges,# of Instruments	21	13
Non-designated Hedges, Notional Amount	160,381	119,186
Non-designated Hedges, Estimated Fair Value	(139)	(160)
Webster Position Commercial Loan Interest Rate Swaps One [Member]
Derivative [Line Items]
Non-designated Hedges,# of Instruments	149	119
Non-designated Hedges, Notional Amount	849,562	595,542
Non-designated Hedges, Estimated Fair Value	(46,562)	(40,269)
Webster Position Commercial Loan Interest Rate Swaps Two [Member]
Derivative [Line Items]
Non-designated Hedges,# of Instruments	1	4
Non-designated Hedges, Notional Amount	34,000	20,180
Non-designated Hedges, Estimated Fair Value	55	13
Webster Position Commercial Loan Interest Rate Swaps With Floors [Member]
Derivative [Line Items]
Non-designated Hedges,# of Instruments	11	12
Non-designated Hedges, Notional Amount	23,396	25,217
Non-designated Hedges, Estimated Fair Value	(1,754)	(1,597)
Webster Position Commercial Loan Interest Rate Caps [Member]
Derivative [Line Items]
Non-designated Hedges,# of Instruments	21	13
Non-designated Hedges, Notional Amount	160,381	119,186
Non-designated Hedges, Estimated Fair Value	$ 139	$ 160