Fair Market Value of Financial Assets and Liabilities, Quantitative Information about Level 3 Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Mortgage Servicing Rights [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Assets, Fair Value Disclosure	2,652	2,364
Mortgage Servicing Rights [Member] | Minimum [Member]
Fair Value Inputs [Abstract]
Constant prepayment rate (in hundredths)	11.40%	8.50%
Probability of default (in hundredths)	0.55%	1.02%
Mortgage Servicing Rights [Member] | Maximum [Member]
Fair Value Inputs [Abstract]
Constant prepayment rate (in hundredths)	21.40%	25.00%
Probability of default (in hundredths)	4.71%	4.81%
Mortgage Servicing Rights [Member] | Weighted Average [Member]
Fair Value Inputs [Abstract]
Constant prepayment rate (in hundredths)	(15.10%)	16.30%
Probability of default (in hundredths)	(2.73%)	2.65%
Discount rate (in hundredths)	(10.50%)	10.50%
Impaired Loans (Collateral Dependent) [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Assets, Fair Value Disclosure	2,326	5,465
Impaired Loans (Collateral Dependent) [Member] | Minimum [Member]
Fair Value Inputs [Abstract]
Marketability discount (in hundredths)	5.00%	5.00%
Impaired Loans (Collateral Dependent) [Member] | Maximum [Member]
Fair Value Inputs [Abstract]
Marketability discount (in hundredths)	10.00%	10.00%
Impaired Loans (Collateral Dependent) [Member] | Weighted Average [Member]
Fair Value Inputs [Abstract]
Marketability discount (in hundredths)	(7.00%)	7.00%
Other Real Estate/Asset Owned [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Assets, Fair Value Disclosure	4,365	13,892
Other Real Estate/Asset Owned [Member] | Minimum [Member]
Fair Value Inputs [Abstract]
Comparability adjustments (in hundredths)	5.00%	5.00%
Other Real Estate/Asset Owned [Member] | Maximum [Member]
Fair Value Inputs [Abstract]
Comparability adjustments (in hundredths)	57.00%	35.00%
Other Real Estate/Asset Owned [Member] | Weighted Average [Member]
Fair Value Inputs [Abstract]
Comparability adjustments (in hundredths)	(24.00%)	13.00%