Allowance For Loan Losses, Allowance For Losses On Lending-Related Commitments And Impaired Loans (Summary Of Impaired Loans, Including Restructured Loans) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012		Dec. 31, 2011		Mar. 31, 2011
Financing Receivable, Impaired [Line Items]
Total impaired loans	$ 251,963	[1]	$ 226,538	[1]	$ 203,536	[1]
Allowance for loan losses related to impaired loans	20,989		21,488		25,615
Restructured loans	165,046		130,518		96,569
Impaired Loans With No Related ASC 310 Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans	114,158		110,759		103,801
Impaired Loans With A Related ASC 310 Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans	$ 137,805	[2]	$ 115,779	[2]	$ 99,735	[2]

[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] 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.