Fair Value (Assets Measured at Fair Value on Nonrecurring Basis) (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure, nonrecurring	$ 12,211	$ 11,014
Fair value measured on nonrecurring basis losses	10,405	13,646
Impaired loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure, nonrecurring	9,592	7,819
Fair value measured on nonrecurring basis losses	10,586	13,893
Other real estate owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure, nonrecurring	2,619	3,195
Fair value measured on nonrecurring basis losses	(181)	(247)
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure, nonrecurring	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Impaired loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure, nonrecurring	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Other real estate owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure, nonrecurring	0	0
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure, nonrecurring	0	0
Significant Other Observable Inputs (Level 2) | Impaired loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure, nonrecurring	0	0
Significant Other Observable Inputs (Level 2) | Other real estate owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure, nonrecurring	0	0
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure, nonrecurring	12,211	11,014
Significant Unobservable Inputs (Level 3) | Impaired loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure, nonrecurring	9,592	7,819
Significant Unobservable Inputs (Level 3) | Other real estate owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure, nonrecurring	$ 2,619	$ 3,195