Allowance For Loan Losses and Credit Quality Information (Consumer credit exposure credit risk profile based on payment activity) (Detail) (USD $)	Sep. 30, 2012		Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonperforming	$ 2,701,759,000		$ 2,755,669,000
Nonperforming	100.00%		100.00%
Troubled debt restructured mortgages and home equity installment loans	22,300,000		27,700,000
Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructured mortgages and home equity installment loans	10,200,000		8,900,000
Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonperforming	250,342,000		275,503,000
Residential [Member] | Nonperforming Financing Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonperforming	18,072,000	[1]	16,227,000	[1]
Residential [Member] | Performing Financing Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonperforming	232,270,000		259,276,000
Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonperforming	283,485,000		291,757,000
Consumer [Member] | Nonperforming Financing Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonperforming	6,694,000	[1]	2,621,000	[1]
Consumer [Member] | Performing Financing Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonperforming	276,791,000		289,136,000
Residential And Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonperforming	533,827,000		567,260,000
Nonperforming	100.00%		100.00%
Residential And Consumer Loan [Member] | Nonperforming Financing Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonperforming	24,766,000	[1]	18,848,000	[1]
Nonperforming	5.00%	[1]	3.00%	[1]
Residential And Consumer Loan [Member] | Performing Financing Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonperforming	$ 509,061,000		$ 548,412,000
Nonperforming	95.00%		97.00%

[1] Includes $10.2 million at September 30, 2012 and $8.9 million at December 31, 2011 of troubled debt restructured mortgages and home equity installment loans performing in accordance with modified terms and are accruing interest