Loans and Allowance for Loan Losses, Allowance for Credit Losses (Details) (USD $)	3 Months Ended			12 Months Ended
	Mar. 31, 2014		Mar. 31, 2013	Dec. 31, 2013
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	$ 67,523,575			$ 67,969,693
Changes in allowance for loan losses [Roll Forward]
Beginning Balance	67,970,000		69,417,000	69,417,000
Charged-off loans	(1,503,511)		(3,557,313)	(17,252,000)
Recovery of previously charged-off loans	568,000			7,948,000
Provision for loan losses	488,000			7,857,000
Ending Balance	67,524,000			67,970,000
Financing Receivable, Individually Evaluated for Impairment	30,713,000			37,829,000
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	7,010,000			3,973,000
Financing Receivable, Collectively Evaluated for Impairment	4,150,974,000			4,106,664,000
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	60,514,000			59,755,000
Financing Receivable, Acquired with Deteriorated Credit Quality	0			0
Financing Receivable, Allowance for Credit Losses, Acquired with Deteriorated Credit Quality	0			0
Loans and Leases Receivable, Net of Deferred Income	4,181,686,799			4,144,493,486
Loans and other extensions of credit granted to directors, executive officers, and their related entities	10,200,000			11,200,000
Amount drawn from loans and other extensions of credit granted	7,700,000			8,900,000
Mortgage loans held-for-sale	13,970,926			12,850,339
Gain loss on sale of loans held for sale	952,200		1,800,000
Commercial Real Estate - Mortgage [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	20,550,000			21,372,000
Changes in allowance for loan losses [Roll Forward]
Beginning Balance	21,372,000		19,634,000	19,634,000
Charged-off loans	(123,000)			(4,123,000)
Recovery of previously charged-off loans	1,000			500,000
Provision for loan losses	(700,000)			5,361,000
Ending Balance	20,550,000			21,372,000
Financing Receivable, Individually Evaluated for Impairment	15,024,000			22,470,000
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	914,000			2,074,000
Financing Receivable, Collectively Evaluated for Impairment	1,441,148,000			1,360,965,000
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	19,636,000			19,298,000
Financing Receivable, Acquired with Deteriorated Credit Quality	0			0
Financing Receivable, Allowance for Credit Losses, Acquired with Deteriorated Credit Quality				0
Loans and Leases Receivable, Net of Deferred Income	1,456,172,000			1,383,435,000
Consumer Real Estate - Mortgage [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	7,822,000			8,355,000
Changes in allowance for loan losses [Roll Forward]
Beginning Balance	8,355,000		8,762,000	8,762,000
Charged-off loans	(334,000)			(2,250,000)
Recovery of previously charged-off loans	72,000			1,209,000
Provision for loan losses	(271,000)			634,000
Ending Balance	7,822,000			8,355,000
Financing Receivable, Individually Evaluated for Impairment	9,649,000			9,273,000
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	1,396,000			1,265,000
Financing Receivable, Collectively Evaluated for Impairment	693,943,000			686,343,000
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	6,426,000			7,090,000
Financing Receivable, Acquired with Deteriorated Credit Quality	0			0
Financing Receivable, Allowance for Credit Losses, Acquired with Deteriorated Credit Quality				0
Loans and Leases Receivable, Net of Deferred Income	703,592,000			695,616,000
Construction and Land Development [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	6,765,000			7,235,000
Changes in allowance for loan losses [Roll Forward]
Beginning Balance	7,235,000		9,164,000	9,164,000
Charged-off loans	(7,000)			(1,351,000)
Recovery of previously charged-off loans	31,000			1,464,000
Provision for loan losses	(494,000)			(2,042,000)
Ending Balance	6,765,000			7,235,000
Financing Receivable, Individually Evaluated for Impairment	1,101,000			1,183,000
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	28,000			49,000
Financing Receivable, Collectively Evaluated for Impairment	292,954,000			315,008,000
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	6,737,000			7,186,000
Financing Receivable, Acquired with Deteriorated Credit Quality	0			0
Financing Receivable, Allowance for Credit Losses, Acquired with Deteriorated Credit Quality				0
Loans and Leases Receivable, Net of Deferred Income	294,055,000			316,191,000
Commercial and Industrial [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	26,710,000			25,134,000
Changes in allowance for loan losses [Roll Forward]
Beginning Balance	25,134,000		24,738,000	24,738,000
Charged-off loans	(824,000)			(8,159,000)
Recovery of previously charged-off loans	398,000			4,531,000
Provision for loan losses	2,002,000			4,024,000
Ending Balance	26,710,000			25,134,000
Financing Receivable, Individually Evaluated for Impairment	4,399,000			4,385,000
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	759,000			474,000
Financing Receivable, Collectively Evaluated for Impairment	1,564,538,000			1,601,162,000
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	25,951,000			24,660,000
Financing Receivable, Acquired with Deteriorated Credit Quality	0			0
Financing Receivable, Allowance for Credit Losses, Acquired with Deteriorated Credit Quality				0
Loans and Leases Receivable, Net of Deferred Income	1,568,937,000			1,605,547,000
Consumer and Other [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	1,886,000			1,632,000
Changes in allowance for loan losses [Roll Forward]
Beginning Balance	1,632,000		1,094,000	1,094,000
Charged-off loans	(214,000)			(1,369,000)
Recovery of previously charged-off loans	66,000			244,000
Provision for loan losses	402,000			1,663,000
Ending Balance	1,886,000			1,632,000
Financing Receivable, Individually Evaluated for Impairment	540,000			518,000
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	122,000			111,000
Financing Receivable, Collectively Evaluated for Impairment	158,391,000			143,186,000
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	1,764,000			1,521,000
Financing Receivable, Acquired with Deteriorated Credit Quality	0			0
Financing Receivable, Allowance for Credit Losses, Acquired with Deteriorated Credit Quality				0
Loans and Leases Receivable, Net of Deferred Income	158,931,000			143,704,000
Unallocated [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	3,791,000			4,242,000
Changes in allowance for loan losses [Roll Forward]
Beginning Balance	4,242,000		6,025,000	6,025,000
Charged-off loans	0			0
Recovery of previously charged-off loans	0			0
Provision for loan losses	(451,000)			(1,783,000)
Ending Balance	3,791,000			4,242,000
Accruing Loans [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	60,514,000			59,755,000
Changes in allowance for loan losses [Roll Forward]
Loans and Leases Receivable, Net of Deferred Income	4,150,974,000			4,106,664,000
Accruing Loans [Member] | Commercial Real Estate - Mortgage [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	19,636,000			19,298,000
Changes in allowance for loan losses [Roll Forward]
Loans and Leases Receivable, Net of Deferred Income	1,441,148,000			1,360,965,000
Accruing Loans [Member] | Consumer Real Estate - Mortgage [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	6,426,000			7,090,000
Changes in allowance for loan losses [Roll Forward]
Loans and Leases Receivable, Net of Deferred Income	693,943,000			686,343,000
Accruing Loans [Member] | Construction and Land Development [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	6,737,000			7,186,000
Changes in allowance for loan losses [Roll Forward]
Loans and Leases Receivable, Net of Deferred Income	292,954,000			315,008,000
Accruing Loans [Member] | Commercial and Industrial [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	25,951,000			24,660,000
Changes in allowance for loan losses [Roll Forward]
Loans and Leases Receivable, Net of Deferred Income	1,564,538,000			1,601,162,000
Accruing Loans [Member] | Consumer and Other [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	1,764,000			1,521,000
Changes in allowance for loan losses [Roll Forward]
Loans and Leases Receivable, Net of Deferred Income	158,391,000			143,186,000
Accruing 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]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	1,298,000			1,187,000
Changes in allowance for loan losses [Roll Forward]
Loans and Leases Receivable, Net of Deferred Income	15,606,000			18,183,000
Nonaccrual Loans [Member] | Commercial Real Estate - Mortgage [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	161,000			142,000
Changes in allowance for loan losses [Roll Forward]
Loans and Leases Receivable, Net of Deferred Income	7,145,000			9,017,000
Nonaccrual Loans [Member] | Consumer Real Estate - Mortgage [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	875,000			722,000
Changes in allowance for loan losses [Roll Forward]
Loans and Leases Receivable, Net of Deferred Income	5,679,000			5,289,000
Nonaccrual Loans [Member] | Construction and Land Development [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	14,000			33,000
Changes in allowance for loan losses [Roll Forward]
Loans and Leases Receivable, Net of Deferred Income	990,000			1,070,000
Nonaccrual Loans [Member] | Commercial and Industrial [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	162,000			218,000
Changes in allowance for loan losses [Roll Forward]
Loans and Leases Receivable, Net of Deferred Income	1,538,000			2,565,000
Nonaccrual Loans [Member] | Consumer and Other [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	86,000			72,000
Changes in allowance for loan losses [Roll Forward]
Loans and Leases Receivable, Net of Deferred Income	254,000			242,000
Nonaccrual Loans [Member] | Unallocated [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	0			0
Troubled Debt Restructurings [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	1,921,000	[1]		2,786,000	[1]
Changes in allowance for loan losses [Roll Forward]
Loans and Leases Receivable, Net of Deferred Income	15,107,000	[2]		19,646,000	[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	753,000	[1]		1,932,000	[1]
Changes in allowance for loan losses [Roll Forward]
Loans and Leases Receivable, Net of Deferred Income	7,879,000	[2]		13,453,000	[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	521,000	[1]		543,000	[1]
Changes in allowance for loan losses [Roll Forward]
Loans and Leases Receivable, Net of Deferred Income	3,970,000	[2]		3,984,000	[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	14,000	[1]		16,000	[1]
Changes in allowance for loan losses [Roll Forward]
Loans and Leases Receivable, Net of Deferred Income	111,000	[2]		113,000	[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	597,000	[1]		256,000	[1]
Changes in allowance for loan losses [Roll Forward]
Loans and Leases Receivable, Net of Deferred Income	2,861,000	[2]		1,820,000	[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	36,000	[1]		39,000	[1]
Changes in allowance for loan losses [Roll Forward]
Loans and Leases Receivable, Net of Deferred Income	286,000	[2]		276,000	[2]
Troubled Debt Restructurings [Member] | Unallocated [Member]
Allowance allocation by loan classification for accruing and impaired loans [Abstract]
Total Allowance for Loan Losses	$ 0	[1]		$ 0	[1]

[1] Troubled debt restructurings of $15.1 million and $19.6 million as of March 31, 2014 and December 31, 2013, respectively, are classified as impaired loans pursuant to U.S. GAAP; however, these loans continue to accrue interest at contractual rates.

[2] Troubled debt restructurings are presented as an impaired loan; however, they continue to accrue interest at contractual rates