Fair Value of Assets and Liabilities (Details 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Interest Rate Lock Commitments | Pricing Model
Summary of the significant unobservable inputs
Weighted Average Closing Ratio (as a percent)	89.79%	88.86%
Net Derivative Financial Instruments Not Designated as Hedging Instruments, at Fair Value	$ 5,206	$ 10,188
Interest Rate Swap Agreements | Discounted cash flow valuation technique
Summary of the significant unobservable inputs
Weighted Average Credit Factor (as a percent)	0.76%	0.77%
Net Derivative Financial Instruments Not Designated as Hedging Instruments, at Fair Value	(228)	(248)
Mortgage Servicing Rights | Discounted cash flow valuation technique
Summary of the significant unobservable inputs
Weighted Average Constant Prepayment Rate (as a percent)	10.80%	12.26%
Weighted Average Discount Rate (as a percent)	5.85%	5.57%
Mortgage Servicing Rights Unobservable Inputs	$ 31,000	$ 27,904