Fair Value Measurements (Details 3) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Assets:
Impaired Loans	$ 70,267,000	$ 73,646,000
Assumptions used in discounted cash flow model to determine fair value of investments classified within level 3
Charges to allowance for probable loan losses in connection with other real estate owned	61,000	10,450,000
Adjustment to fair value in connection with other real estate owned	(70,000)	0
Impaired commercial collateral dependent loans	70,267,000	73,646,000
Impaired commerical collateral dependent receivables appraisals to determine fair value within last twelve months	50,579,000	48,856,000
Significant Unobservable Inputs (Level 3) | Bond meeting the original contract terms
Assumptions used in discounted cash flow model to determine fair value of investments classified within level 3
Estimated future principal prepayment rate assumption, low end of range (as a percent)	7.00%
Estimated future principal prepayment rate assumption, discount rate (as a percent)	13.00%
Default rate assumptions (as a percent)	1.00%
Loss severity rate assumptions, first year (as a percent)	25.00%
Significant Unobservable Inputs (Level 3) | Bond not meeting the original contract terms
Assumptions used in discounted cash flow model to determine fair value of investments classified within level 3
Estimated future principal prepayment rate assumption, low end of range (as a percent)	2.00%
Estimated future principal prepayment rate assumption, discount rate (as a percent)	13.00%
Default rate assumptions (as a percent)	4.50%
Loss severity rate assumptions, first year (as a percent)	60.00%
Decrease in loss severity rates, following five years (as a percent)	5.00%
Loss severity rate, thereafter (as a percent)	25.00%
Measured on a non-recurring basis:
Assumptions used in discounted cash flow model to determine fair value of investments classified within level 3
Change in net provision (Credit), impaired loans	10,332,000	295,000
Change in net provision (Credit), other real estate owned	(70,000)
Measured on a non-recurring basis: | Assets/Liabilities Measured at Fair Value
Assets:
Impaired Loans	27,330,000	11,981,000
Non-financial assets:
Other real estate owned	2,752,000	18,749,000
Assumptions used in discounted cash flow model to determine fair value of investments classified within level 3
Impaired commercial collateral dependent loans	27,330,000	11,981,000
Measured on a non-recurring basis: | Significant Unobservable Inputs (Level 3)
Assets:
Impaired Loans	27,330,000	11,981,000
Non-financial assets:
Other real estate owned	2,752,000	18,749,000
Assumptions used in discounted cash flow model to determine fair value of investments classified within level 3
Impaired commercial collateral dependent loans	$ 27,330,000	$ 11,981,000