Regulatory Matters (Information On The Capital Ratios) (Detail) (USD $)	9 Months Ended
	Sep. 30, 2012 Y	Sep. 30, 2011	Dec. 31, 2011	Sep. 30, 2012 Webster Capital Trust IV [Member]	Jul. 18, 2012 Webster Capital Trust IV [Member]	Dec. 31, 2011 Webster Capital Trust IV [Member]	Sep. 30, 2012 Webster Financial Corporation [Member]	Dec. 31, 2011 Webster Financial Corporation [Member]	Sep. 30, 2012 Webster Bank, N.A. [Member]	Dec. 31, 2011 Webster Bank, N.A. [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total risk-based capital, Actual Amount							$ 1,722,253,000	$ 1,766,468,000	$ 1,691,800,000	$ 1,681,769,000
Total risk-based capital, Actual Ratio							13.20%	14.60%	13.00%	14.00%
Total risk-based capital, Capital Requirements Amount							1,047,193,000	967,017,000	1,044,669,000	964,184,000
Total risk-based capital, Capital Requirements Ratio							8.00%	8.00%	8.00%	8.00%
Total risk-based capital, Well Capitalized Amount							1,308,991,000	1,208,772,000	1,305,836,000	1,205,230,000
Total risk-based capital, Well Capitalized Ratio							10.00%	10.00%	10.00%	10.00%
Tier 1 capital, Actual Amount							1,557,359,000	1,577,991,000	1,528,224,000	1,494,529,000
Tier 1 capital, Actual Ratio							11.90%	13.10%	11.70%	12.40%
Tier 1 capital, Capital Requirements Amount							523,596,000	483,509,000	522,334,000	482,092,000
Tier 1 capital, Capital Requirements Ratio							4.00%	4.00%	4.00%	4.00%
Tier 1 capital, Well Capitalized Amount							785,395,000	725,263,000	783,502,000	723,138,000
Tier 1 capital, Well Capitalized Ratio							6.00%	6.00%	6.00%	6.00%
Tier 1 leverage capital ratio, Actual Amount							1,557,359,000	1,577,991,000	1,528,224,000	1,494,529,000
Tier 1 leverage capital ratio, Actual Ratio							8.20%	8.90%	8.10%	8.40%
Tier 1 leverage capital ratio, Capital Requirements Amount							756,176,000	713,319,000	754,935,000	711,572,000
Tier 1 leverage capital ratio, Capital Requirements Ratio							4.00%	4.00%	4.00%	4.00%
Tier 1 leverage capital ratio, Well Capitalized Amount							945,220,000	891,648,000	943,668,000	889,466,000
Tier 1 leverage capital ratio, Well Capitalized Ratio							5.00%	5.00%	5.00%	5.00%
Dividends paid by Webster Bank	110,000,000	125,000,000
Preceding period of retained net profits, years	2
Webster Capital Trust IV Preferred securities	$ 77,320,000		$ 213,390,000	$ 0	$ 136,100,000	$ 136,070,000
Stated interest rate	7.65%			7.65%