Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Modifications [Line Items]
Financing Receivable Impaired Troubled Debt Restructuring Return To Performing Status	$ 5,500,000	$ 16,600,000	$ 25,700,000
TDRs Restructured Loans, valuation allowance	2,000,000	2,800,000
Accrued TDRs	27,853,000	17,791,000	47,706,000
Commitments to lend additional funds TDRs	180,000	0
Special Mention and Substandard Loans
Financing Receivable, Modifications [Line Items]
Accrued TDRs	$ 2,800,000	$ 448,000