Loans and Allowance for Loan Losses, Allowance for Credit Losses (Details) (USD $)	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	$ 69,417,437		$ 73,974,675
Changes in allowance for loan losses [Roll Forward]
Beginning Balance	73,975,000		82,575,000		91,959,000
Charged-off loans	(19,657,061)		(34,849,910)		(67,543,395)
Recovery of previously charged-off loans	9,530,000		4,452,000		4,464,000
Provision for loan losses	5,569,000		21,798,000		53,695,000
Ending Balance	69,417,000		73,975,000		82,575,000
Loans and other extensions of credit granted to directors, executive officers, and their related entities	8,800,000		10,800,000
Amount drawn from loans and other extensions of credit granted	8,100,000		9,600,000
Mortgage loans held-for-sale	41,194,639		35,363,038
Gain loss on sale of loans held for sale	6,700,000		4,100,000		4,100,000
Number of mortgage loans sold to third party	13,000
Mortgage loans sold	2,821,000,000
Number of conventional loans underwritten	3,300
Percentage of loan to value (in hundredths)	80.00%
Number of loans underwritten	2,800
Home equity and consumer mortgage loans	679,900,000
Commercial and Industrial [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	24,738,000		20,789,000
Changes in allowance for loan losses [Roll Forward]
Beginning Balance	20,789,000		21,426,000		26,332,000
Charged-off loans	(4,612,000)		(15,360,000)		(23,555,000)
Recovery of previously charged-off loans	7,175,000	[1]	2,167,000		874,000
Provision for loan losses	1,386,000		12,556,000		17,775,000
Ending Balance	24,738,000		20,789,000		21,426,000
Construction and Land Development [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	9,164,000		12,040,000
Changes in allowance for loan losses [Roll Forward]
Beginning Balance	12,040,000		19,122,000		23,027,000
Charged-off loans	(2,530,000)		(10,157,000)		(27,526,000)
Recovery of previously charged-off loans	1,155,000		1,530,000		2,618,000
Provision for loan losses	(1,501,000)		1,545,000		21,003,000
Ending Balance	9,164,000		12,040,000		19,122,000
Unallocated [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	6,025,000		6,322,000
Changes in allowance for loan losses [Roll Forward]
Beginning Balance	6,322,000		11,003,000		6,914,000
Charged-off loans	0		0		0
Recovery of previously charged-off loans	0		0		0
Provision for loan losses	(297,000)		(4,681,000)		4,089,000
Ending Balance	6,025,000		6,322,000		11,003,000
Consumer Real Estate - Mortgage [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	8,762,000		10,302,000
Changes in allowance for loan losses [Roll Forward]
Beginning Balance	10,302,000		9,898,000		10,725,000
Charged-off loans	(6,731,000)		(5,076,000)		(6,769,000)
Recovery of previously charged-off loans	818,000		495,000		377,000
Provision for loan losses	4,373,000		4,985,000		5,565,000
Ending Balance	8,762,000		10,302,000		9,898,000
Commercial Real Estate - Mortgage [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	19,634,000		23,397,000
Changes in allowance for loan losses [Roll Forward]
Beginning Balance	23,397,000		19,252,000		22,505,000
Charged-off loans	(4,667,000)		(3,044,000)		(9,041,000)
Recovery of previously charged-off loans	285,000		116,000		343,000
Provision for loan losses	619,000		7,073,000		5,445,000
Ending Balance	19,634,000		23,397,000		19,252,000
Consumer and Other [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	1,094,000		1,125,000
Changes in allowance for loan losses [Roll Forward]
Beginning Balance	1,125,000		1,874,000		2,456,000
Charged-off loans	(1,117,000)		(1,213,000)		(652,000)
Recovery of previously charged-off loans	97,000		144,000		252,000
Provision for loan losses	989,000		320,000		(182,000)
Ending Balance	1,094,000		1,125,000		1,874,000
Accruing Loans [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	57,815,000		59,607,000
Accruing Loans [Member] | Commercial and Industrial [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	23,829,000		17,740,000
Accruing Loans [Member] | Construction and Land Development [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	8,953,000		10,764,000
Accruing Loans [Member] | Unallocated [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	0		0
Accruing Loans [Member] | Consumer Real Estate - Mortgage [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	7,336,000		9,485,000
Accruing Loans [Member] | Commercial Real Estate - Mortgage [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	16,642,000		20,581,000
Accruing Loans [Member] | Consumer and Other [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	1,055,000		1,037,000
Nonaccrual Loans [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	1,764,000		4,440,000
Nonaccrual Loans [Member] | Commercial and Industrial [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	814,000		2,767,000
Nonaccrual Loans [Member] | Construction and Land Development [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	201,000		1,264,000
Nonaccrual Loans [Member] | Unallocated [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	0		0
Nonaccrual Loans [Member] | Consumer Real Estate - Mortgage [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	573,000		301,000
Nonaccrual Loans [Member] | Commercial Real Estate - Mortgage [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	154,000		57,000
Nonaccrual Loans [Member] | Consumer and Other [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	22,000		51,000
Troubled Debt Restructurings [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	3,813,000	[2]	3,606,000	[2]
Troubled Debt Restructurings [Member] | Commercial and Industrial [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	95,000	[2]	282,000	[2]
Troubled Debt Restructurings [Member] | Construction and Land Development [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	10,000	[2]	12,000	[2]
Troubled Debt Restructurings [Member] | Unallocated [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	0	[2]	0	[2]
Troubled Debt Restructurings [Member] | Consumer Real Estate - Mortgage [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	853,000	[2]	516,000	[2]
Troubled Debt Restructurings [Member] | Commercial Real Estate - Mortgage [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	2,838,000	[2]	2,759,000	[2]
Troubled Debt Restructurings [Member] | Consumer and Other [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	$ 17,000	[2]	$ 37,000	[2]

[1] Includes the 2012 $5.6 million recovery of a loan previously charged off in 2009.

[2] Troubled debt restructurings of $27.5 million and $23.4 million as of December 31, 2012 and 2011, respectively, are classified as impaired loans pursuant to U.S. GAAP; however, these loans continue to accrue interest at contractual rates.