CONSOLIDATED STATEMENTS OF OPERATIONS (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Interest income:
Loans, including fees	$ 160,036,709	$ 154,748,491	$ 162,901,763
Securities:
Taxable	16,931,417	23,971,787	30,306,189
Tax-exempt	6,576,701	7,394,134	7,916,596
Federal funds sold and other	1,876,731	2,232,423	2,223,816
Total interest income	185,421,558	188,346,835	203,348,364
Interest expense:
Deposits	16,842,852	30,588,033	49,856,815
Securities sold under agreements to repurchase	455,499	1,110,078	1,749,905
Federal Home Loan Bank advances and other borrowings	5,258,749	5,184,313	7,368,258
Total interest expense	22,557,100	36,882,424	58,974,978
Net interest income	162,864,458	151,464,411	144,373,386
Provision for loan losses	5,568,830	21,797,613	53,695,454
Net interest income after provision for loan losses	157,295,628	129,666,798	90,677,932
Noninterest income:
Service charges on deposit accounts	9,917,754	9,244,165	9,591,543
Investment services	6,984,970	6,246,414	5,050,105
Insurance sales commissions	4,461,404	3,999,153	3,864,340
Trust fees	3,195,950	2,999,731	2,872,490
Gains on mortgage loans sold, net	6,698,618	4,155,137	4,085,657
Net gain on sale of investment securities	2,150,605	960,763	2,623,674
Other noninterest income	9,987,335	10,334,847	8,227,237
Total noninterest income	43,396,636	37,940,210	36,315,046
Noninterest expense:
Salaries and employee benefits	78,056,564	74,424,851	64,628,991
Equipment and occupancy	20,420,333	19,986,976	21,077,223
Other real estate expense	11,544,067	17,431,926	29,210,197
Marketing and other business development	3,635,810	3,303,151	3,233,224
Postage and supplies	2,379,730	2,120,722	2,538,021
Amortization of intangibles	2,738,994	2,862,837	2,980,986
Other noninterest expense	19,389,368	18,976,865	23,214,670
Total noninterest expense	138,164,866	139,107,328	146,883,312
Income (loss) before income taxes	62,527,398	28,499,680	(19,890,334)
Income tax expense (benefit)	20,643,517	(15,237,687)	4,410,158
Net income (loss)	41,883,881	43,737,367	(24,300,492)
Preferred stock dividends	1,660,868	4,606,493	4,815,973
Accretion on preferred stock discount	2,153,172	2,058,146	1,326,049
Net income (loss) available to common stockholders	$ 38,069,841	$ 37,072,728	$ (30,442,514)
Per share information:
Basic net income (loss) per common share available to common stockholders (in dollars per share)	$ 1.12	$ 1.11	$ (0.93)
Diluted net income (loss) per common share available to common stockholders (in dollars per share)	$ 1.10	$ 1.09	$ (0.93)
Weighted average common shares outstanding:
Basic (in shares)	33,899,667	33,420,015	32,789,871
Diluted (in shares)	34,487,808	34,060,228	32,789,871