Disclosures About Fair Value of Financial Instruments - Fair value measurements of assets on recurring basis (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Available-for-sale securities
Investment securities available for sale	$ 126,308	$ 113,770
Fair Value | Fair Value, Measurements, Recurring
Available-for-sale securities
Investment securities available for sale	126,308	113,770
Fair Value | Fair Value, Measurements, Recurring | Federal agencies
Available-for-sale securities
Investment securities available for sale	44,940	43,409
Fair Value | Fair Value, Measurements, Recurring | State and municipal
Available-for-sale securities
Investment securities available for sale	34,386	31,162
Fair Value | Fair Value, Measurements, Recurring | Government-sponsored enterprise (GSE) residential mortgage-backed and other asset-backed agency securities
Available-for-sale securities
Investment securities available for sale	44,264	36,022
Fair Value | Fair Value, Measurements, Recurring | Corporate
Available-for-sale securities
Investment securities available for sale	2,718	3,177
Fair Value Measurements Using Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Measurements, Recurring
Available-for-sale securities
Investment securities available for sale
Fair Value Measurements Using Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Measurements, Recurring | Federal agencies
Available-for-sale securities
Investment securities available for sale
Fair Value Measurements Using Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Measurements, Recurring | State and municipal
Available-for-sale securities
Investment securities available for sale
Fair Value Measurements Using Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Measurements, Recurring | Government-sponsored enterprise (GSE) residential mortgage-backed and other asset-backed agency securities
Available-for-sale securities
Investment securities available for sale
Fair Value Measurements Using Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Measurements, Recurring | Corporate
Available-for-sale securities
Investment securities available for sale
Fair Value Measurements Using Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring
Available-for-sale securities
Investment securities available for sale	125,087	112,573
Fair Value Measurements Using Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Federal agencies
Available-for-sale securities
Investment securities available for sale	44,940	43,409
Fair Value Measurements Using Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | State and municipal
Available-for-sale securities
Investment securities available for sale	34,386	31,162
Fair Value Measurements Using Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Government-sponsored enterprise (GSE) residential mortgage-backed and other asset-backed agency securities
Available-for-sale securities
Investment securities available for sale	44,264	36,022
Fair Value Measurements Using Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Corporate
Available-for-sale securities
Investment securities available for sale	1,497	1,980
Fair Value Measurements Using Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring
Available-for-sale securities
Investment securities available for sale	1,221	1,197
Fair Value Measurements Using Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Federal agencies
Available-for-sale securities
Investment securities available for sale
Fair Value Measurements Using Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | State and municipal
Available-for-sale securities
Investment securities available for sale
Fair Value Measurements Using Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Government-sponsored enterprise (GSE) residential mortgage-backed and other asset-backed agency securities
Available-for-sale securities
Investment securities available for sale
Fair Value Measurements Using Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Corporate
Available-for-sale securities
Investment securities available for sale	$ 1,221	$ 1,197