Business Segments - Operating Results and Total Assets Reportable Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 Segment	Sep. 30, 2011	Dec. 31, 2011
Segment Reporting Information [Line Items]
Number of business segments			4
Percentage of provision expense attributable to business segments	76.80%		65.70%
Net interest income	$ 144,890	$ 141,685	$ 432,636	$ 422,759
(Benefit) provision for loan and lease losses	5,000	5,000	14,000	20,000
Net interest income after provision for loan and lease losses	139,890	136,685	418,636	402,759
Non-interest income	48,479	44,691	139,818	134,796
Non-interest expense	123,887	123,218	378,879	384,404
Income from continuing operations before income tax expense	64,482	58,158	179,575	153,151
Income tax expense (benefit)	19,489	15,927	54,404	44,152
Income (loss) from continuing operations		42,231		108,999
Income from discontinued operations				1,995
Net income	44,993	42,231	125,171	110,994
Less: Net loss attributable to noncontrolling interests	0	0	0	(1)
Net income attributable to Webster Financial Corporation	44,993	42,231	125,171	110,995
Total assets	19,729,662		19,729,662		18,714,340
Commercial Banking [Member]
Segment Reporting Information [Line Items]
Net interest income	48,127	43,511	137,610	124,810
(Benefit) provision for loan and lease losses	(5,540)	(6,989)	(10,979)	(14,230)
Net interest income after provision for loan and lease losses	53,667	50,500	148,589	139,040
Non-interest income	7,191	5,838	21,365	18,527
Non-interest expense	24,935	24,216	74,662	79,195
Income from continuing operations before income tax expense	35,923	32,122	95,292	78,372
Income tax expense (benefit)	10,859	8,852	28,870	22,594
Income (loss) from continuing operations		23,270		55,778
Income from discontinued operations
Net income		23,270		55,778
Less: Net loss attributable to noncontrolling interests
Net income attributable to Webster Financial Corporation	25,064	23,270	66,422	55,778
Total assets	4,819,511		4,819,511		4,359,405
Retail Banking [Member]
Segment Reporting Information [Line Items]
Net interest income	59,639	60,301	175,258	171,706
(Benefit) provision for loan and lease losses	1,019	5,912	3,163	12,936
Net interest income after provision for loan and lease losses	58,620	54,389	172,095	158,770
Non-interest income	23,098	26,226	67,292	76,864
Non-interest expense	66,076	68,253	201,809	208,866
Income from continuing operations before income tax expense	15,642	12,362	37,578	26,768
Income tax expense (benefit)	4,731	3,437	11,385	7,717
Income (loss) from continuing operations		8,925		19,051
Income from discontinued operations
Net income		8,925		19,051
Less: Net loss attributable to noncontrolling interests
Net income attributable to Webster Financial Corporation	10,911	8,925	26,193	19,051
Total assets	1,604,029		1,604,029		1,546,457
Consumer Finance [Member]
Segment Reporting Information [Line Items]
Net interest income	26,661	26,459	80,735	80,729
(Benefit) provision for loan and lease losses	8,690	12,026	17,684	25,445
Net interest income after provision for loan and lease losses	17,971	14,433	63,051	55,284
Non-interest income	7,214	2,907	17,093	7,096
Non-interest expense	18,377	18,648	55,623	56,768
Income from continuing operations before income tax expense	6,808	(1,308)	24,521	5,612
Income tax expense (benefit)	2,055	(438)	7,429	1,618
Income (loss) from continuing operations		(870)		3,994
Income from discontinued operations
Net income		(870)		3,994
Less: Net loss attributable to noncontrolling interests				(1)
Net income attributable to Webster Financial Corporation	4,753	(870)	17,092	3,995
Total assets	5,957,594		5,957,594		5,869,028
Other Segments [Member]
Segment Reporting Information [Line Items]
Net interest income	8,526	6,678	24,824	18,352
(Benefit) provision for loan and lease losses	(328)	245	(668)	11
Net interest income after provision for loan and lease losses	8,854	6,433	25,492	18,341
Non-interest income	7,139	5,960	21,553	17,847
Non-interest expense	10,993	9,900	33,275	29,758
Income from continuing operations before income tax expense	5,000	2,493	13,770	6,430
Income tax expense (benefit)	1,512	684	4,172	1,854
Income (loss) from continuing operations		1,809		4,576
Income from discontinued operations
Net income		1,809		4,576
Less: Net loss attributable to noncontrolling interests
Net income attributable to Webster Financial Corporation	3,488	1,809	9,598	4,576
Total assets	273,214		273,214		245,554
Total Business Segments [Member]
Segment Reporting Information [Line Items]
Net interest income	142,953	136,949	418,427	395,597
(Benefit) provision for loan and lease losses	3,841	11,194	9,200	24,162
Net interest income after provision for loan and lease losses	139,112	125,755	409,227	371,435
Non-interest income	44,642	40,931	127,303	120,334
Non-interest expense	120,381	121,017	365,369	374,587
Income from continuing operations before income tax expense	63,373	45,669	171,161	117,182
Income tax expense (benefit)	19,157	12,535	51,856	33,783
Income (loss) from continuing operations		33,134		83,399
Income from discontinued operations
Net income		33,134		83,399
Less: Net loss attributable to noncontrolling interests				(1)
Net income attributable to Webster Financial Corporation	44,216	33,134	119,305	83,400
Total assets	12,654,348		12,654,348		12,020,444
Corporate And Reconciling [Member]
Segment Reporting Information [Line Items]
Net interest income	1,937	4,736	14,209	27,162
(Benefit) provision for loan and lease losses	1,159	(6,194)	4,800	(4,162)
Net interest income after provision for loan and lease losses	778	10,930	9,409	31,324
Non-interest income	3,837	3,760	12,515	14,462
Non-interest expense	3,506	2,201	13,510	9,817
Income from continuing operations before income tax expense	1,109	12,489	8,414	35,969
Income tax expense (benefit)	332	3,392	2,548	10,369
Income (loss) from continuing operations		9,097		25,600
Income from discontinued operations				1,995
Net income		9,097		27,595
Less: Net loss attributable to noncontrolling interests
Net income attributable to Webster Financial Corporation	777	9,097	5,866	27,595
Total assets	$ 7,075,314		$ 7,075,314		$ 6,693,896