Allowance For Loan Losses, Allowance For Losses On Lending-Related Commitments And Impaired Loans (Summary Of Impaired Loans, Including Restructured Loans) (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011		Sep. 30, 2011
Total impaired loans	$ 233,014	[1]	$ 226,538	[1]	$ 203,570	[1]
Allowance for loan losses related to impaired loans	19,818		21,488		28,447
Restructured loans	114,404	[2],[3]			73,838	[2],[3]
Impaired Loans With A Related ASC 310 Allowance Recorded [Member]
Total impaired loans	120,060	[4]	115,779	[4]	83,191	[4]
Impaired Financing Receivables With No Related Allowance [Member]
Total impaired loans	112,954		110,759		120,379
Restructured Loans [Member]
Restructured loans	$ 147,196		$ 130,518		$ 104,392

[1] Impaired loans are considered by the Company to be non-accrual loans, restructured loans or loans with principal and/or interest at risk, even if the loan is current with all payments of principal and interest.

[2] Balances represent the recorded investment in the loan at the time of the restructuring.

[3] Total restructured loans represent all loans restructured during the previous twelve months from the date indicated.

[4] These impaired loans require an allowance for loan losses because the estimated fair value of the loans or related collateral is less than the recorded investment in the loans.