Fair Values of Assets and Liabilities - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets, Level 1 to Level 2 Transfers, Description	$ 0		$ 0		$ 0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0	$ 0	536,000	$ 0
Impaired loans considered to be credit risk of non-collection	100,000		100,000
Updated appraisal requirement floor	250,000		250,000
Other real estate owned	7,686,000		7,686,000		9,398,000
Financial instrument of credit risk	200,000		200,000		$ 200,000
Fair Value, Assets Measured on Recurring Basis, Gain (Loss) Included in Other Income, Assets and Liabilities Continue to be held			0	$ 0
Other Assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	$ 0		$ 536,000
Minimum [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Swap Rates Term Used to Determine Yield Curve			3 years
Maximum [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Swap Rates Term Used to Determine Yield Curve			30 years