Business Segments - Operating Results and Total Assets Reportable Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013 Segment	Dec. 31, 2012 Segment	Dec. 31, 2011
Segment Reporting Information [Line Items]
Number of Reportable Segments									3	4
Percentage of provision expense attributable to business segments									115.40%	83.70%	108.80%
Net interest income (loss)	$ 153,884	$ 149,987	$ 147,061	$ 145,796	$ 146,272	$ 144,890	$ 144,378	$ 143,368	$ 596,728	$ 578,908	$ 563,768
Provision (benefit) charged to expense	9,000	8,500	8,500	7,500	7,500	5,000	5,000	4,000	33,500	21,500	22,500
Net interest income after provision for loan and lease losses									563,228	557,408	541,268
Non-interest income									191,050	192,758	177,042
Non-interest expense	126,639	122,281	123,604	125,535	122,925	123,887	127,179	127,813	498,059	501,804	510,976
Income from continuing operations before income tax expense	62,509	65,463	67,208	61,039	68,787	64,482	59,552	55,541	256,219	248,362	207,334
Income tax expense (benefit)	18,755	18,158	20,835	18,922	20,261	19,489	18,312	16,603	76,670	74,665	57,951
Income from continuing operations									179,549	173,697	149,383
Income from discontinued operations, net of tax									0	0	1,995
Net income									179,549	173,697	151,378
Less: Net loss attributable to noncontrolling interests									0	0	(1)
Net income attributable to Webster Financial Corporation	43,754	47,305	46,373	42,117	48,526	44,993	41,240	38,938	179,549	173,697	151,379
Total Assets	20,852,999				20,146,765				20,852,999	20,146,765	18,714,340
Commercial Banking [Member]
Segment Reporting Information [Line Items]
Net interest income (loss)									217,582	188,666	168,560
Provision (benefit) charged to expense									18,581	(7,498)	(21,213)
Net interest income after provision for loan and lease losses									199,001	196,164	189,773
Non-interest income									30,797	29,324	25,869
Non-interest expense									99,801	98,718	105,356
Income from continuing operations before income tax expense									129,997	126,770	110,286
Income tax expense (benefit)									38,900	38,111	30,826
Income from continuing operations											79,460
Income from discontinued operations, net of tax											0
Net income											79,460
Less: Net loss attributable to noncontrolling interests											0
Net income attributable to Webster Financial Corporation									91,097	88,659	79,460
Total Assets	5,682,129				5,113,898				5,682,129	5,113,898	4,359,403
Community Banking [Member]
Segment Reporting Information [Line Items]
Net interest income (loss)									347,395	342,268	340,519
Provision (benefit) charged to expense									19,973	26,167	45,293
Net interest income after provision for loan and lease losses									327,422	316,101	295,226
Non-interest income									116,182	116,978	108,212
Non-interest expense									337,795	340,907	356,443
Income from continuing operations before income tax expense									105,809	92,172	46,995
Income tax expense (benefit)									31,662	27,710	13,135
Income from continuing operations											33,860
Income from discontinued operations, net of tax											0
Net income											33,860
Less: Net loss attributable to noncontrolling interests											(1)
Net income attributable to Webster Financial Corporation									74,147	64,462	33,861
Total Assets	7,809,343				7,708,159				7,809,343	7,708,159	7,415,480
Other [Member]
Segment Reporting Information [Line Items]
Net interest income (loss)									40,992	33,308	25,437
Provision (benefit) charged to expense									93	(680)	398
Net interest income after provision for loan and lease losses									40,899	33,988	25,039
Non-interest income									32,926	28,680	24,199
Non-interest expense									49,745	44,649	40,387
Income from continuing operations before income tax expense									24,080	18,019	8,851
Income tax expense (benefit)									7,205	5,417	2,474
Income from continuing operations											6,377
Income from discontinued operations, net of tax											0
Net income											6,377
Less: Net loss attributable to noncontrolling interests											0
Net income attributable to Webster Financial Corporation									16,875	12,602	6,377
Total Assets	365,863				282,414				365,863	282,414	245,554
Segment Totals [Member]
Segment Reporting Information [Line Items]
Net interest income (loss)									605,969	564,242	534,516
Provision (benefit) charged to expense									38,647	17,989	24,478
Net interest income after provision for loan and lease losses									567,322	546,253	510,038
Non-interest income									179,905	174,982	158,280
Non-interest expense									487,341	484,274	502,186
Income from continuing operations before income tax expense									259,886	236,961	166,132
Income tax expense (benefit)									77,767	71,238	46,435
Income from continuing operations											119,697
Income from discontinued operations, net of tax											0
Net income											119,697
Less: Net loss attributable to noncontrolling interests											(1)
Net income attributable to Webster Financial Corporation									182,119	165,723	119,698
Total Assets	13,857,335				13,104,471				13,857,335	13,104,471	12,020,437
Corporate and Reconciling [Member]
Segment Reporting Information [Line Items]
Net interest income (loss)									(9,241)	14,666	29,252
Provision (benefit) charged to expense									(5,147)	3,511	(1,978)
Net interest income after provision for loan and lease losses									(4,094)	11,155	31,230
Non-interest income									11,145	17,776	18,762
Non-interest expense									10,718	17,530	8,790
Income from continuing operations before income tax expense									(3,667)	11,401	41,202
Income tax expense (benefit)									(1,097)	3,427	11,516
Income from continuing operations											29,686
Income from discontinued operations, net of tax											1,995
Net income											31,681
Less: Net loss attributable to noncontrolling interests											0
Net income attributable to Webster Financial Corporation									(2,570)	7,974	31,681
Total Assets	$ 6,995,664				$ 7,042,294				$ 6,995,664	$ 7,042,294	$ 6,693,903