Subsequent Event (Detail) (USD $)	0 Months Ended	9 Months Ended
Feb. 08, 2012	Sep. 30, 2012	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]
Subsequent Events [Line Items]
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%
Accrued and unpaid interest paid from cash on hand	$ 77,800,000	$ 137,000,000

Carrying value as of the balance sheet date of long-term debt (with maturities initially due after one year or beyond the operating cycle if longer) identified as Junior Subordinated Notes, which have a lower priority than senior instruments, excluding current portion.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

Name:	us-gaap_JuniorSubordinatedLongTermNotes
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant