Disclosures About Fair Value of Financial Instruments - Fair value measurements of assets and liabilities on nonrecurring basis (Details 2) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Real estate, held for sale	$ 1,934	$ 1,610
Fair Value | Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	1,233	4,363
Real estate, held for sale	248	700
Fair Value Measurements Using Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans
Real estate, held for sale
Fair Value Measurements Using Significant Other Observable Inputs ( Level 2) | Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans
Real estate, held for sale
Fair Value Measurements Using Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	1,233	4,363
Real estate, held for sale	$ 248	$ 700