Past Due Loans, Allowance For Credit Losses, Impaired Loans, and TDRs (Detail) - Narrative - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Modifications [Line Items]
Valuation allowance on troubled debt restructured loans	$ 758	$ 1,800
Commitments to lend additional funds TDRs		666
Accruing
Financing Receivable, Modifications [Line Items]
Total value of TDRs returned to performing status	0	20,656	$ 5,529
Special Mention and Substandard Loans
Financing Receivable, Modifications [Line Items]
Accruing	$ 862	$ 1,800