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 ($) $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance				$ 83,575				$ 67,240				$ 58,980	$ 83,575	$ 67,240	$ 58,980
Charged-off loans													(28,467)	(30,400)	(22,046)
Recovery of previously charged-off loans													12,386	12,358	6,642
Provision for loan losses	$ 4,644	$ 8,260	$ 7,195	7,184	$ 9,319	$ 8,725	$ 9,402	6,931	$ 6,281	$ 6,920	$ 6,812	3,651	27,283	34,377	23,664
Ending Balance	94,777				83,575				67,240				94,777	83,575	67,240
Collectively Evaluated for Impairment	90,512				78,934				63,147				90,512	78,934	63,147
Individually Evaluated for Impairment	3,280				3,964				2,198				3,280	3,964	2,198
Ending Balance	94,777				83,575				67,240				94,777	83,575	67,240
Collectively Evaluated for Impairment	19,708,817				17,599,074				15,531,482				19,708,817	17,599,074	15,531,482
Individually Evaluated for Impairment	58,144				83,146				58,979				58,144	83,146	58,979
Loans acquired with deteriorated credit quality	20,915				25,329				42,655				20,915	25,329	42,655
Loans	19,787,876				17,707,549				15,633,116				19,787,876	17,707,549	15,633,116
Currently performing impaired loans	35,800				52,500								35,800	52,500
Financial Asset Acquired with Credit Deterioration
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Individually Evaluated for Impairment	0				0				573				0	0	573
Commercial Real Estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance				26,946				21,188				13,655	26,946	21,188	13,655
Charged-off loans													(1,700)	(3,030)	(633)
Recovery of previously charged-off loans													2,232	2,096	671
Provision for loan losses													5,891	6,692	7,495
Ending Balance	33,369				26,946				21,188				33,369	26,946	21,188
Collectively Evaluated for Impairment	32,134				26,222				20,753				32,134	26,222	20,753
Individually Evaluated for Impairment	1,235				724				95				1,235	724	95
Ending Balance	33,369				26,946				21,188				33,369	26,946	21,188
Collectively Evaluated for Impairment	7,681,608				7,124,117				6,630,593				7,681,608	7,124,117	6,630,593
Individually Evaluated for Impairment	18,122				28,838				18,214				18,122	28,838	18,214
Loans acquired with deteriorated credit quality	9,488				11,999				20,803				9,488	11,999	20,803
Loans	7,709,218				7,164,954				6,669,610				7,709,218	7,164,954	6,669,610
Commercial Real Estate | Financial Asset Acquired with Credit Deterioration
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Individually Evaluated for Impairment	0				0				340				0	0	340
Consumer Real Estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance				7,670				5,031				6,564	7,670	5,031	6,564
Charged-off loans													(1,335)	(1,593)	(1,461)
Recovery of previously charged-off loans													1,827	2,653	1,516
Provision for loan losses													(108)	1,579	(1,588)
Ending Balance	8,054				7,670				5,031				8,054	7,670	5,031
Collectively Evaluated for Impairment	6,762				6,227				4,460				6,762	6,227	4,460
Individually Evaluated for Impairment	1,292				1,443				410				1,292	1,443	410
Ending Balance	8,054				7,670				5,031				8,054	7,670	5,031
Collectively Evaluated for Impairment	3,036,922				2,808,142				2,534,996				3,036,922	2,808,142	2,534,996
Individually Evaluated for Impairment	25,018				27,111				12,172				25,018	27,111	12,172
Loans acquired with deteriorated credit quality	6,685				9,194				14,046				6,685	9,194	14,046
Loans	3,068,625				2,844,447				2,561,214				3,068,625	2,844,447	2,561,214
Consumer Real Estate | Financial Asset Acquired with Credit Deterioration
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Individually Evaluated for Impairment	0				0				161				0	0	161
Construction and Land Development
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance				11,128				8,962				3,624	11,128	8,962	3,624
Charged-off loans													(18)	(74)	(137)
Recovery of previously charged-off loans													682	1,863	1,136
Provision for loan losses													870	377	4,339
Ending Balance	12,662				11,128				8,962				12,662	11,128	8,962
Collectively Evaluated for Impairment	12,629				11,100				8,879				12,629	11,100	8,879
Individually Evaluated for Impairment	33				28				66				33	28	66
Ending Balance	12,662				11,128				8,962				12,662	11,128	8,962
Collectively Evaluated for Impairment	2,426,901				2,066,613				1,896,553				2,426,901	2,066,613	1,896,553
Individually Evaluated for Impairment	561				2,367				5,167				561	2,367	5,167
Loans acquired with deteriorated credit quality	3,021				3,475				6,568				3,021	3,475	6,568
Loans	2,430,483				2,072,455				1,908,288				2,430,483	2,072,455	1,908,288
Construction and Land Development | Financial Asset Acquired with Credit Deterioration
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Individually Evaluated for Impairment	0				0				17				0	0	17
Commercial and Industrial
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance				31,731				24,863				24,743	31,731	24,863	24,743
Charged-off loans													(19,208)	(13,175)	(4,297)
Recovery of previously charged-off loans													6,473	3,035	1,317
Provision for loan losses													17,116	17,008	3,100
Ending Balance	36,112				31,731				24,863				36,112	31,731	24,863
Collectively Evaluated for Impairment	35,401				30,290				23,181				35,401	30,290	23,181
Individually Evaluated for Impairment	711				1,441				1,627				711	1,441	1,627
Ending Balance	36,112				31,731				24,863				36,112	31,731	24,863
Collectively Evaluated for Impairment	6,274,280				5,246,913				4,116,677				6,274,280	5,246,913	4,116,677
Individually Evaluated for Impairment	14,295				23,847				23,426				14,295	23,847	23,426
Loans acquired with deteriorated credit quality	1,721				661				1,238				1,721	661	1,238
Loans	6,290,296				5,271,421				4,141,341				6,290,296	5,271,421	4,141,341
Commercial and Industrial | Financial Asset Acquired with Credit Deterioration
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Individually Evaluated for Impairment	0				0				55				0	0	55
Consumer and Other
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance				5,423				5,874				9,520	5,423	5,874	9,520
Charged-off loans													(6,206)	(12,528)	(15,518)
Recovery of previously charged-off loans													1,172	2,711	2,002
Provision for loan losses													3,206	9,366	9,870
Ending Balance	3,595				5,423				5,874				3,595	5,423	5,874
Collectively Evaluated for Impairment	3,586				5,095				5,874				3,586	5,095	5,874
Individually Evaluated for Impairment	9				328				0				9	328	0
Ending Balance	3,595				5,423				5,874				3,595	5,423	5,874
Collectively Evaluated for Impairment	289,106				353,289				352,663				289,106	353,289	352,663
Individually Evaluated for Impairment	148				983				0				148	983	0
Loans acquired with deteriorated credit quality	0				0				0				0	0	0
Loans	289,254				354,272				352,663				289,254	354,272	352,663
Consumer and Other | Financial Asset Acquired with Credit Deterioration
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Individually Evaluated for Impairment	0				0				0				0	0	0
Unallocated Financing Receivables
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance				$ 677				$ 1,322				$ 874	677	1,322	874
Charged-off loans													0		0
Recovery of previously charged-off loans													0		0
Provision for loan losses													308	(645)	448
Ending Balance	985				677				1,322				985	677	1,322
Ending Balance	$ 985				$ 677				$ 1,322				$ 985	$ 677	$ 1,322