Loans and Allowance for Loan Losses Loans and Allowance for Loan Losses - Details on Allowance for Loan Losses and Recorded Investment by Loan Classification (Details) - USD ($)	3 Months Ended												12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance				$ 58,980,000				$ 65,432,000				$ 67,359,000	$ 58,980,000	$ 65,432,000	$ 67,359,000
Charged-off loans													(22,046,511)	(31,112,118)	(21,148,034)
Recovery of previously charged-off loans													6,642,000	6,332,000	10,033,000
Provision for loan losses	$ 6,281,000	$ 6,920,000	$ 6,812,000	3,651,000	$ 3,046,000	$ 6,108,000	$ 5,280,000	3,894,000	$ 5,459,000	$ 2,228,000	$ 1,186,000	315,000	23,663,944	18,328,058	9,188,497
Ending Balance	67,240,000				58,980,000				65,432,000				67,240,000	58,980,000	65,432,000
Collectively Evaluated for Impairment	63,147,000				57,014,000				59,730,000				63,147,000	57,014,000	59,730,000
Individually Evaluated for Impairment	2,198,000				1,092,000				5,165,000				2,198,000	1,092,000	5,165,000
Ending Balance	67,240,000				58,980,000				65,432,000				67,240,000	58,980,000	65,432,000
Collectively Evaluated for Impairment	15,531,482,000				8,407,338,000				6,505,788,000				15,531,482,000	8,407,338,000	6,505,788,000
Individually Evaluated for Impairment	58,979,000				33,750,000				25,313,000				58,979,000	33,750,000	25,313,000
Loans acquired with deteriorated credit quality	42,655,000				8,837,000				12,134,000				42,655,000	8,837,000	12,134,000
Loans	15,633,116,029				8,449,924,736				6,543,235,000				15,633,116,029	8,449,924,736	6,543,235,000
Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Individually Evaluated for Impairment	573,000				0				0				573,000	0	0
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance				13,655,000				15,513,000				22,202,000	13,655,000	15,513,000	22,202,000
Charged-off loans													(633,000)	(276,000)	(384,000)
Recovery of previously charged-off loans													671,000	208,000	85,000
Provision for loan losses													7,495,000	(1,790,000)	(6,390,000)
Ending Balance	21,188,000				13,655,000				15,513,000				21,188,000	13,655,000	15,513,000
Collectively Evaluated for Impairment	20,753,000				13,595,000				15,452,000				20,753,000	13,595,000	15,452,000
Individually Evaluated for Impairment	95,000				60,000				61,000				95,000	60,000	61,000
Ending Balance	21,188,000				13,655,000				15,513,000				21,188,000	13,655,000	15,513,000
Collectively Evaluated for Impairment	6,630,593,000				3,188,361,000				2,269,439,000				6,630,593,000	3,188,361,000	2,269,439,000
Individually Evaluated for Impairment	18,214,000				2,750,000				2,420,000				18,214,000	2,750,000	2,420,000
Loans acquired with deteriorated credit quality	20,803,000				2,385,000				3,624,000				20,803,000	2,385,000	3,624,000
Loans	6,669,610,000				3,193,496,000				2,275,483,000				6,669,610,000	3,193,496,000	2,275,483,000
Commercial Real Estate [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Individually Evaluated for Impairment	340,000				0				0				340,000	0	0
Residential Mortgage [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance				6,564,000				7,220,000				5,424,000	6,564,000	7,220,000	5,424,000
Charged-off loans													(1,461,000)	(788,000)	(365,000)
Recovery of previously charged-off loans													1,516,000	546,000	874,000
Provision for loan losses													(1,588,000)	(414,000)	1,287,000
Ending Balance	5,031,000				6,564,000				7,220,000				5,031,000	6,564,000	7,220,000
Collectively Evaluated for Impairment	4,460,000				5,874,000				6,109,000				4,460,000	5,874,000	6,109,000
Individually Evaluated for Impairment	410,000				690,000				1,111,000				410,000	690,000	1,111,000
Ending Balance	5,031,000				6,564,000				7,220,000				5,031,000	6,564,000	7,220,000
Collectively Evaluated for Impairment	2,534,996,000				1,174,456,000				1,033,479,000				2,534,996,000	1,174,456,000	1,033,479,000
Individually Evaluated for Impairment	12,172,000				8,941,000				8,986,000				12,172,000	8,941,000	8,986,000
Loans acquired with deteriorated credit quality	14,046,000				2,520,000				4,052,000				14,046,000	2,520,000	4,052,000
Loans	2,561,214,000				1,185,917,000				1,046,517,000				2,561,214,000	1,185,917,000	1,046,517,000
Residential Mortgage [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Individually Evaluated for Impairment	161,000				0				0				161,000	0	0
Construction and Land Development [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance				3,624,000				2,903,000				5,724,000	3,624,000	2,903,000	5,724,000
Charged-off loans													(137,000)	(231,000)	(190,000)
Recovery of previously charged-off loans													1,136,000	545,000	1,479,000
Provision for loan losses													4,339,000	407,000	(4,110,000)
Ending Balance	8,962,000				3,624,000				2,903,000				8,962,000	3,624,000	2,903,000
Collectively Evaluated for Impairment	8,879,000				3,604,000				2,891,000				8,879,000	3,604,000	2,891,000
Individually Evaluated for Impairment	66,000				20,000				12,000				66,000	20,000	12,000
Ending Balance	8,962,000				3,624,000				2,903,000				8,962,000	3,624,000	2,903,000
Collectively Evaluated for Impairment	1,896,553,000				906,053,000				740,090,000				1,896,553,000	906,053,000	740,090,000
Individually Evaluated for Impairment	5,167,000				3,212,000				3,689,000				5,167,000	3,212,000	3,689,000
Loans acquired with deteriorated credit quality	6,568,000				3,408,000				3,918,000				6,568,000	3,408,000	3,918,000
Loans	1,908,288,000				912,673,000				747,697,000				1,908,288,000	912,673,000	747,697,000
Construction and Land Development [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Individually Evaluated for Impairment	17,000				0				0				17,000	0	0
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance				24,743,000				23,643,000				29,167,000	24,743,000	23,643,000	29,167,000
Charged-off loans													(4,297,000)	(5,801,000)	(2,207,000)
Recovery of previously charged-off loans													1,317,000	2,138,000	1,730,000
Provision for loan losses													3,100,000	4,763,000	(5,047,000)
Ending Balance	24,863,000				24,743,000				23,643,000				24,863,000	24,743,000	23,643,000
Collectively Evaluated for Impairment	23,181,000				24,648,000				22,669,000				23,181,000	24,648,000	22,669,000
Individually Evaluated for Impairment	1,627,000				95,000				974,000				1,627,000	95,000	974,000
Ending Balance	24,863,000				24,743,000				23,643,000				24,863,000	24,743,000	23,643,000
Collectively Evaluated for Impairment	4,116,677,000				2,872,855,000				2,222,714,000				4,116,677,000	2,872,855,000	2,222,714,000
Individually Evaluated for Impairment	23,426,000				18,331,000				5,288,000				23,426,000	18,331,000	5,288,000
Loans acquired with deteriorated credit quality	1,238,000				524,000				540,000				1,238,000	524,000	540,000
Loans	4,141,341,000				2,891,710,000				2,228,542,000				4,141,341,000	2,891,710,000	2,228,542,000
Commercial and Industrial [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Individually Evaluated for Impairment	55,000				0				0				55,000	0	0
Consumer and Other [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance				9,520,000				15,616,000				1,570,000	9,520,000	15,616,000	1,570,000
Charged-off loans													(15,518,000)	(24,016,000)	(18,002,000)
Recovery of previously charged-off loans													2,002,000	2,895,000	5,865,000
Provision for loan losses													9,870,000	15,025,000	26,183,000
Ending Balance	5,874,000				9,520,000				15,616,000				5,874,000	9,520,000	15,616,000
Collectively Evaluated for Impairment	5,874,000				9,293,000				12,609,000				5,874,000	9,293,000	12,609,000
Individually Evaluated for Impairment	0				227,000				3,007,000				0	227,000	3,007,000
Ending Balance	5,874,000				9,520,000				15,616,000				5,874,000	9,520,000	15,616,000
Collectively Evaluated for Impairment	352,663,000				265,613,000				240,066,000				352,663,000	265,613,000	240,066,000
Individually Evaluated for Impairment	0				516,000				4,930,000				0	516,000	4,930,000
Loans acquired with deteriorated credit quality	0				0				0				0	0	0
Loans	352,663,000				266,129,000				244,996,000				352,663,000	266,129,000	244,996,000
Consumer and Other [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Individually Evaluated for Impairment	0				0				0				0	0	0
Unallocated Financing Receivables [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance				$ 874,000				$ 537,000				$ 3,272,000	874,000	537,000	3,272,000
Charged-off loans													0	0	0
Recovery of previously charged-off loans													0	0	0
Provision for loan losses													448,000	337,000	(2,735,000)
Ending Balance	1,322,000				874,000				537,000				1,322,000	874,000	537,000
Ending Balance	$ 1,322,000				$ 874,000				$ 537,000				$ 1,322,000	$ 874,000	$ 537,000