Allowance For Loan Losses, Allowance For Losses On Lending-Related Commitments And Impaired Loans (Narrative) (Details) (USD $)	3 Months Ended				12 Months Ended
	Mar. 31, 2012		Mar. 31, 2011		Dec. 31, 2011
Restructuring Cost and Reserve [Line Items]
Restructured modified loans	$ 39,683,000	[1]	$ 9,359,000	[1]
Number of credit relationships in modified loans	31	[1]	15	[1]
Collateral impairment reviewed in restructured loan	2,700,000
Weighted average stated interest rate - basis points	162		286
Principal balances that were forgiven			67,000,000,000
Average recorded investment	253,552,000		205,343,000		247,054,000
Interest income recognized on impaired loans	3,149,000		3,211,000		12,470,000
Troubled Debt Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructured modified loans	39,700,000		9,400,000
Number of credit relationships in modified loans	31		15
Restructured Loans [Member]
Restructuring Cost and Reserve [Line Items]
Restructured modified loans	$ 165,000,000
Number of credit relationships in modified loans	182

[1] Restructured loans may have more than one modification representing a concession. As such, restructured loans during the period may be represented in more than one of the categories noted above.