Allowance For Loan Losses, Allowance For Losses On Lending-Related Commitments And Impaired Loans (Narrative) (Detail) (USD $)	3 Months Ended
	Mar. 31, 2013 Loan		Mar. 31, 2012 Loan		Dec. 31, 2012
Troubled Debt Restructuring, Debtor, Subsequent Periods [Line Items]
Restructured loans	$ 116,345,000		$ 165,046,000		$ 126,473,000
Troubled debt restructuring modifications, number of count	58	[1],[2]	139	[1],[2]
Restructured loans	35,106,000	[1],[2]	130,851,000	[1],[2]
Collateral impairment reviewed in restructured loan	2,600,000
Interest income	229,000		238,000
Financing Receivables, Modifications, Weighted Average Extension Term	21 months		7 months
Financing Receivables, Modifications, Weighted Average Interest Only Term	8 months		4 months
Principal balances that were forgiven	50,000		0
Weighted average stated interest rate, basis points	1.53%		1.62%
Restructured Loans [Member]
Troubled Debt Restructuring, Debtor, Subsequent Periods [Line Items]
Troubled debt restructuring modifications, number of count	167
All Modifications [Member]
Troubled Debt Restructuring, Debtor, Subsequent Periods [Line Items]
Troubled debt restructuring modifications, number of count	14	[1],[3]	31	[1],[3]
Restructured loans	$ 2,277,000	[1],[3]	$ 39,683,000	[1],[3]

[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.

[3] 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.