Fair Values of Financial Instruments - Summary of Assets and Liabilities Measured at Fair Value on a Recurring Basis (Detail) (Fair Value, Measurements, Recurring, USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Assets:
Assets estimated fair value	$ 76,617	$ 70,299
Liabilities:
Derivative financial instruments	674	303
Mortgage-backed securities [Member]
Assets:
Assets estimated fair value	49,133	48,246
Obligations of other U. S. government agencies [Member]
Assets:
Assets estimated fair value	6,896	4,360
Obligations of state and political subdivisions [Member]
Assets:
Assets estimated fair value	11,939	11,740
Corporate bonds [Member]
Assets:
Assets estimated fair value	7,834	5,419
Equity securities [Member]
Assets:
Assets estimated fair value	815	534
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Assets:
Assets estimated fair value	815	534
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Equity securities [Member]
Assets:
Assets estimated fair value	815	534
Significant Other Observable Inputs (Level 2) [Member]
Assets:
Assets estimated fair value	75,802	69,765
Liabilities:
Derivative financial instruments	674	303
Significant Other Observable Inputs (Level 2) [Member] | Mortgage-backed securities [Member]
Assets:
Assets estimated fair value	49,133	48,246
Significant Other Observable Inputs (Level 2) [Member] | Obligations of other U. S. government agencies [Member]
Assets:
Assets estimated fair value	6,896	4,360
Significant Other Observable Inputs (Level 2) [Member] | Obligations of state and political subdivisions [Member]
Assets:
Assets estimated fair value	11,939	11,740
Significant Other Observable Inputs (Level 2) [Member] | Corporate bonds [Member]
Assets:
Assets estimated fair value	$ 7,834	$ 5,419