Fair Value - Level 3 Quantitative Information (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Recurring | Interest Rate Swap Agreements | Derivative Financial Instruments, Assets | Weighted Average
Fair Value Inputs
Discount rate	1.00%	1.00%
Recurring | Interest Rate Lock Commitments | Derivative Financial Instruments, Liabilities | Minimum
Fair Value Inputs
Pull through rates	88.00%
Recurring | Interest Rate Lock Commitments | Derivative Financial Instruments, Liabilities | Maximum
Fair Value Inputs
Pull through rates	90.00%
Recurring | Interest Rate Lock Commitments | Derivative Financial Instruments, Liabilities | Weighted Average
Fair Value Inputs
Pull through rates		83.90%
Recurring | Mortgage Servicing Rights | Derivative Financial Instruments, Assets
Fair Value Inputs
Discount rate	8.00%	8.00%
Constant prepayment rate	15.91%	17.96%
Cost of service	50	50
Nonrecurring | Impaired Loans Receivable | Minimum
Fair Value Inputs
Collateral discounts	15.00%	10.00%
Nonrecurring | Impaired Loans Receivable | Maximum
Fair Value Inputs
Collateral discounts	50.00%	15.00%
Nonrecurring | Other Real Estate Owned | Minimum
Fair Value Inputs
Collateral discounts	6.00%
Nonrecurring | Other Real Estate Owned | Maximum
Fair Value Inputs
Collateral discounts	15.00%
Nonrecurring | Other Real Estate Owned | Weighted Average
Fair Value Inputs
Collateral discounts		15.00%
Level 3 | Recurring | Interest Rate Swap Agreements
Quantitative Information
Assets, Fair Value Disclosure	180,000	196,000
Level 3 | Recurring | Interest Rate Lock Commitments
Quantitative Information
Liabilities, Fair Value Disclosure	807,000	873,000
Level 3 | Recurring | Mortgage Servicing Rights
Quantitative Information
Assets, Fair Value Disclosure	3,045,000	2,525,000
Level 3 | Nonrecurring | Impaired Loans Receivable
Quantitative Information
Assets, Fair Value Disclosure	11,145,000	7,276,000
Level 3 | Nonrecurring | Other Real Estate Owned
Quantitative Information
Assets, Fair Value Disclosure	5,449,000	5,281,000