Parent Company Information Parent Company Information (Components of Condensed Cash Flow The Parent Company) (Details) (USD $) In Thousands, unless otherwise specified	0 Months Ended	3 Months Ended				12 Months Ended
	Jun. 08, 2011	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Operating activities:
Income from discontinued operations, net of tax							$ (1,995)	$ (94)
Income from continuing operations		40,384	42,231	34,184	32,584	173,697	149,383	72,164
Adjustments to reconcile net income to net cash used for operating activities:
Excess tax benefits from stock-based compensation						(812)	(392)	(92)
Net cash provided by operating activities						257,082	266,130	336,954
Investing activities:
(Increase) decrease in interest-bearing deposits						(2,143)	(43,251)	337,499
Purchases of available for sale securities						(1,204,079)	(1,305,583)	(1,297,512)
Proceeds from maturities and principal payments of available for sale securities						854,747	545,933	608,710
Proceeds from sale of available for sale securities						148,222	278,757	416,474
Net decrease in loan						(915,435)	(338,037)	(173,635)
Net cash used for investing activities						(1,390,092)	(771,709)	(517,841)
Financing activities:
Repayment of long-term debt						(210,971)	(22,689)	0
Issuance of preferred stock						122,710	0	0
Redemption of preferred stock						0	0	(400,000)
Cash dividends paid to common shareholders						(30,667)	(13,978)	(3,133)
Cash dividends paid to preferred shareholders						(2,460)	(2,460)	(17,223)
Exercise of stock options						996	213	378
Excess tax benefits from stock-based compensation						812	392	92
Warburg investment						0	0	36,440
Common stock issued						560	689	118,359
Common stock repurchased						(53,243)	(1,670)	(1,654)
Common stock warrants repurchased	(14,400)					388	16,285
Net cash provided by financing activities						1,189,336	539,692	169,458
Discontinued Operations:
Operating activities						0	1,995	94
Net cash provided by discontinued operations						0	1,995	94
(Decrease) increase in cash and due from banks						56,326	36,108	(11,335)
Parent Company [Member]
Operating activities:
Net income attributable to Webster Financial Corporation						173,697	151,379	72,255
Income from discontinued operations, net of tax						0	1,995	94
Income from continuing operations						173,697	149,384	72,161
Adjustments to reconcile net income to net cash used for operating activities:
Equity in undistributed earnings of subsidiaries and associated companies						(192,287)	(178,827)	(79,131)
Excess tax benefits from stock-based compensation						(812)	(392)	(92)
Other, net						2,345	27,325	(30,163)
Net cash provided by operating activities						(17,057)	(2,510)	(37,225)
Investing activities:
(Increase) decrease in interest-bearing deposits						(24,081)	(120,133)	400,688
Purchases of available for sale securities						(8,272)	(3,714)	(500)
Proceeds from maturities and principal payments of available for sale securities						775	575	0
Proceeds from sale of available for sale securities						1,073	2,353	750
Net decrease in loan						0	13,000	0
Dividend from subsidiary						140,000	170,000	0
Capital contribution to subsidiary						0	0	(100,000)
Net cash used for investing activities						109,495	62,081	300,938
Financing activities:
Repayment of long-term debt						(136,070)	(22,689)	0
Issuance of preferred stock						122,710	0	0
Redemption of preferred stock						0	0	(400,000)
Cash dividends paid to common shareholders						(30,667)	(13,978)	(3,133)
Cash dividends paid to preferred shareholders						(2,460)	(2,460)	(17,223)
Exercise of stock options						996	213	378
Excess tax benefits from stock-based compensation						812	392	92
Warburg investment						0	0	36,440
Common stock issued						560	689	118,359
Common stock repurchased						(53,243)	(1,670)	(1,654)
Common stock warrants repurchased						(388)	(16,285)	0
Net cash provided by financing activities						(97,750)	(55,788)	(266,741)
Discontinued Operations:
Operating activities						0	1,995	94
Net cash provided by discontinued operations						0	1,995	94
(Decrease) increase in cash and due from banks						(5,312)	5,778	(2,934)
Cash and due from banks at beginning of year					9,625	15,403	9,625	12,559
Cash and due from banks at end of year		$ 15,403				$ 10,091	$ 15,403	$ 9,625