Allowance For Loan Losses, Allowance For Losses On Lending-Related Commitments And Impaired Loans (Narrative) (Detail) (USD $)	3 Months Ended				9 Months Ended							3 Months Ended		9 Months Ended
	Sep. 30, 2012 Loan		Sep. 30, 2011 Loan		Sep. 30, 2012 Loan		Sep. 30, 2011 Loan		Sep. 30, 2012 Restructured Loans [Member] credits	Dec. 31, 2011 Restructured Loans [Member]	Sep. 30, 2011 Restructured Loans [Member]	Sep. 30, 2012 Troubled Debt Restructuring [Member] Loan	Sep. 30, 2011 Troubled Debt Restructuring [Member] Loan	Sep. 30, 2012 Troubled Debt Restructuring [Member]	Sep. 30, 2011 Troubled Debt Restructuring [Member] Loan
Troubled Debt Restructuring, Debtor, Subsequent Periods [Line Items]
Restructured loans	$ 114,404,000	[1],[2]	$ 73,838,000	[1],[2]	$ 114,404,000	[1],[2]	$ 73,838,000	[1],[2]	$ 147,196,000	$ 130,518,000	$ 104,392,000
Troubled Debt Restructuring Modifications Number Of Count	121	[1],[2]	91	[1],[2]	121	[1],[2]	91	[1],[2]	181
Number of credit relationships in modified loans (in credits)												18	26	68	70
Collateral impairment reviewed in restructured loan	3,100,000				3,100,000
Interest income	534,000				1,000,000
Restructured modified loans												9,500,000	13,500,000	69,900,000	56,000,000
Financing Receivables, Modifications, Weighted Average Extension Term	8 months		14 months		8 months		10 months
Financing Receivables, Modifications, Weighted Average Interest Only Term	9 months		11 months		5 months		10 months
Principal balances that were forgiven	$ 0		$ 0		$ 420,000		$ 67,000
Weighted Average Stated Interest Rate Basis Points	2.93%		2.01%		1.51%		2.01%

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

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