Fair Value Measurements (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended			3 Months Ended
	Dec. 31, 2012	Mar. 31, 2013 Significant Unobservable Inputs (Level 3) Fair Value measured on a Non-Recurring Basis	Dec. 31, 2012 Significant Unobservable Inputs (Level 3) Fair Value measured on a Non-Recurring Basis	Mar. 31, 2013 Significant Unobservable Inputs (Level 3) Fair Value measured on a Non-Recurring Basis Impaired loans
Collateral-dependent impaired loans	$ 2,437	$ 344	$ 2,437	$ 344
Foreclosed assets	$ 16		$ 16
Valuation Technique	Market comparable properties			Market comparable properties
Unobservable Input	Selling Costs			Selling Costs; Sheriff's sale discount
Range (Weighted Average)	Selling Costs: 10%			Selling Costs: 10%; Sheriff's sale discount 37%