Loans - Aging analysis of past due loans Prior to adoption of ASU 2016-13 (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019
Loans and Allowance for Loan Losses
Past due	$ 31,718
Current	25,095,203
Non-Accruing	110,894
Total loans		$ 11,375,104	$ 11,290,147
30 days past due
Loans and Allowance for Loan Losses
Past due	21,605
60 days past due
Loans and Allowance for Loan Losses
Past due	8,571
90 days past due
Loans and Allowance for Loan Losses
Past due	1,542
Construction and land development
Loans and Allowance for Loan Losses
Past due	2,273
Current	1,836,193
Non-Accruing	1,645
Total loans		1,017,261	1,025,387
Construction and land development | 30 days past due
Loans and Allowance for Loan Losses
Past due	2,028
Construction and land development | 60 days past due
Loans and Allowance for Loan Losses
Past due	245
Consumer Owner Occupied Loans
Loans and Allowance for Loan Losses
Past due	6,679
Current	4,271,410
Non-Accruing	33,097
Total loans		2,706,960	2,760,126
Consumer Owner Occupied Loans | 30 days past due
Loans and Allowance for Loan Losses
Past due	2,184
Consumer Owner Occupied Loans | 60 days past due
Loans and Allowance for Loan Losses
Past due	4,494
Consumer Owner Occupied Loans | 90 days past due
Loans and Allowance for Loan Losses
Past due	1
Other income producing property
Loans and Allowance for Loan Losses
Past due	1,261
Current	620,112
Non-Accruing	8,124
Total loans		346,554	361,879
Other income producing property | 30 days past due
Loans and Allowance for Loan Losses
Past due	1,261
Other loans
Loans and Allowance for Loan Losses
Current	7,540
Total loans		13,892	1,457
Commercial loans | Commercial non-owner occupied
Loans and Allowance for Loan Losses
Past due	625
Current	5,928,700
Non-Accruing	7,047
Total loans		2,323,967	2,357,730
Commercial loans | Commercial non-owner occupied | 30 days past due
Loans and Allowance for Loan Losses
Past due	604
Commercial loans | Commercial non-owner occupied | 60 days past due
Loans and Allowance for Loan Losses
Past due	21
Commercial loans | Commercial owner occupied real estate loan
Loans and Allowance for Loan Losses
Past due	2,535
Current	4,812,672
Non-Accruing	30,813
Commercial loans | Commercial owner occupied real estate loan | 30 days past due
Loans and Allowance for Loan Losses
Past due	1,150
Commercial loans | Commercial owner occupied real estate loan | 60 days past due
Loans and Allowance for Loan Losses
Past due	859
Commercial loans | Commercial owner occupied real estate loan | 90 days past due
Loans and Allowance for Loan Losses
Past due	526
Commercial loans | Commercial and industrial
Loans and Allowance for Loan Losses
Past due	12,867
Current	5,393,529
Non-Accruing	12,724
Total loans		1,386,327	1,261,527
Commercial loans | Commercial and industrial | 30 days past due
Loans and Allowance for Loan Losses
Past due	10,728
Commercial loans | Commercial and industrial | 60 days past due
Loans and Allowance for Loan Losses
Past due	1,507
Commercial loans | Commercial and industrial | 90 days past due
Loans and Allowance for Loan Losses
Past due	632
Consumer | Home equity loans
Loans and Allowance for Loan Losses
Past due	2,852
Current	1,333,516
Non-Accruing	11,430
Total loans		758,020	773,363
Consumer | Home equity loans | 30 days past due
Loans and Allowance for Loan Losses
Past due	1,997
Consumer | Home equity loans | 60 days past due
Loans and Allowance for Loan Losses
Past due	476
Consumer | Home equity loans | 90 days past due
Loans and Allowance for Loan Losses
Past due	379
Consumer | Consumer
Loans and Allowance for Loan Losses
Past due	2,626
Current	891,531
Non-Accruing	6,014
Total loans		663,422	654,883
Consumer | Consumer | 30 days past due
Loans and Allowance for Loan Losses
Past due	1,653
Consumer | Consumer | 60 days past due
Loans and Allowance for Loan Losses
Past due	969
Consumer | Consumer | 90 days past due
Loans and Allowance for Loan Losses
Past due	$ 4
Non-acquired loans
Loans and Allowance for Loan Losses
Past due		10,212	9,754
Current		9,220,317	8,899,904
Non-Accruing		22,302	18,854
Total loans		9,252,831	8,928,512
Non-acquired loans | 30 days past due
Loans and Allowance for Loan Losses
Past due		8,768	6,882
Non-acquired loans | 60 days past due
Loans and Allowance for Loan Losses
Past due		930	2,543
Non-acquired loans | 90 days past due
Loans and Allowance for Loan Losses
Past due		514	329
Non-acquired loans | Construction and land development
Loans and Allowance for Loan Losses
Total loans			955,318
Non-acquired loans | Commercial non-owner occupied
Loans and Allowance for Loan Losses
Total loans			1,777,327
Non-acquired loans | Commercial owner occupied real estate loan
Loans and Allowance for Loan Losses
Total loans			1,677,695
Non-acquired loans | Consumer Owner Occupied Loans
Loans and Allowance for Loan Losses
Total loans			2,118,127
Non-acquired loans | Home equity loans
Loans and Allowance for Loan Losses
Total loans			521,744
Non-acquired loans | Commercial and industrial
Loans and Allowance for Loan Losses
Total loans			1,130,847
Non-acquired loans | Other income producing property
Loans and Allowance for Loan Losses
Past due		612	296
Current		217,159	219,981
Non-Accruing		846	680
Total loans		218,617	220,957
Non-acquired loans | Other income producing property | 30 days past due
Loans and Allowance for Loan Losses
Past due		208	115
Non-acquired loans | Other income producing property | 60 days past due
Loans and Allowance for Loan Losses
Past due			181
Non-acquired loans | Other income producing property | 90 days past due
Loans and Allowance for Loan Losses
Past due		404
Non-acquired loans | Consumer
Loans and Allowance for Loan Losses
Total loans			525,040
Non-acquired loans | Other loans
Loans and Allowance for Loan Losses
Past due		28
Current		13,864	1,457
Total loans		13,892	1,457
Non-acquired loans | Other loans | 30 days past due
Loans and Allowance for Loan Losses
Past due		25
Non-acquired loans | Other loans | 60 days past due
Loans and Allowance for Loan Losses
Past due		3
Non-acquired loans | Commercial loans
Loans and Allowance for Loan Losses
Total loans		6,062,991	5,762,144
Non-acquired loans | Commercial loans | Real estate
Loans and Allowance for Loan Losses
Past due		355
Current		967,511
Non-Accruing		494
Total loans		968,360
Non-acquired loans | Commercial loans | Real estate | 30 days past due
Loans and Allowance for Loan Losses
Past due		321
Non-acquired loans | Commercial loans | Real estate | 60 days past due
Loans and Allowance for Loan Losses
Past due		34
Non-acquired loans | Commercial loans | Construction and land development
Loans and Allowance for Loan Losses
Past due			211
Current			954,558
Non-Accruing			549
Total loans		968,360	955,318
Non-acquired loans | Commercial loans | Construction and land development | 30 days past due
Loans and Allowance for Loan Losses
Past due			194
Non-acquired loans | Commercial loans | Construction and land development | 60 days past due
Loans and Allowance for Loan Losses
Past due			17
Non-acquired loans | Commercial loans | Commercial non-owner occupied
Loans and Allowance for Loan Losses
Past due		114	472
Current		1,810,264	1,776,366
Non-Accruing		760	489
Total loans		1,811,138	1,777,327
Non-acquired loans | Commercial loans | Commercial non-owner occupied | 30 days past due
Loans and Allowance for Loan Losses
Past due		114	173
Non-acquired loans | Commercial loans | Commercial non-owner occupied | 90 days past due
Loans and Allowance for Loan Losses
Past due			299
Non-acquired loans | Commercial loans | Commercial owner occupied real estate loan
Loans and Allowance for Loan Losses
Past due		3,771	4,406
Current		1,776,764	1,669,227
Non-Accruing		3,482	4,062
Total loans		1,784,017	1,677,695
Non-acquired loans | Commercial loans | Commercial owner occupied real estate loan | 30 days past due
Loans and Allowance for Loan Losses
Past due		3,218	2,818
Non-acquired loans | Commercial loans | Commercial owner occupied real estate loan | 60 days past due
Loans and Allowance for Loan Losses
Past due		553	1,588
Non-acquired loans | Commercial loans | Commercial and industrial
Loans and Allowance for Loan Losses
Past due		2,307	1,566
Current		1,272,360	1,126,682
Non-Accruing		6,192	2,599
Total loans		1,280,859	1,130,847
Non-acquired loans | Commercial loans | Commercial and industrial | 30 days past due
Loans and Allowance for Loan Losses
Past due		2,097	1,209
Non-acquired loans | Commercial loans | Commercial and industrial | 60 days past due
Loans and Allowance for Loan Losses
Past due		100	327
Non-acquired loans | Commercial loans | Commercial and industrial | 90 days past due
Loans and Allowance for Loan Losses
Past due		110	30
Non-acquired loans | Commercial loans | Other income producing property
Loans and Allowance for Loan Losses
Total loans		218,617	220,957
Non-acquired loans | Consumer
Loans and Allowance for Loan Losses
Total loans		3,189,840	3,166,368
Non-acquired loans | Consumer | Real estate
Loans and Allowance for Loan Losses
Total loans		2,637,467	2,639,871
Non-acquired loans | Consumer | Consumer Owner Occupied Loans
Loans and Allowance for Loan Losses
Past due		752	1,469
Current		2,110,719	2,109,103
Non-Accruing		7,368	7,555
Total loans		2,118,839	2,118,127
Non-acquired loans | Consumer | Consumer Owner Occupied Loans | 30 days past due
Loans and Allowance for Loan Losses
Past due		752	1,390
Non-acquired loans | Consumer | Consumer Owner Occupied Loans | 60 days past due
Loans and Allowance for Loan Losses
Past due			79
Non-acquired loans | Consumer | Home equity loans
Loans and Allowance for Loan Losses
Past due		1,382	662
Current		515,673	519,701
Non-Accruing		1,573	1,381
Total loans		518,628	521,744
Non-acquired loans | Consumer | Home equity loans | 30 days past due
Loans and Allowance for Loan Losses
Past due		1,343	425
Non-acquired loans | Consumer | Home equity loans | 60 days past due
Loans and Allowance for Loan Losses
Past due		39	237
Non-acquired loans | Consumer | Consumer
Loans and Allowance for Loan Losses
Past due		891	672
Current		536,003	522,829
Non-Accruing		1,587	1,539
Total loans		538,481	525,040
Non-acquired loans | Consumer | Consumer | 30 days past due
Loans and Allowance for Loan Losses
Past due		690	558
Non-acquired loans | Consumer | Consumer | 60 days past due
Loans and Allowance for Loan Losses
Past due		201	114
Non-acquired loans | Consumer | Other loans
Loans and Allowance for Loan Losses
Total loans		13,892	1,457
Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Past due		9,664	7,608
Current		1,739,924	1,948,399
Non-Accruing		10,839	9,596
Total loans		1,760,427	1,965,603
Acquired non-credit impaired loans | 30 days past due
Loans and Allowance for Loan Losses
Past due		2,758	6,976
Acquired non-credit impaired loans | 60 days past due
Loans and Allowance for Loan Losses
Past due		6,631	632
Acquired non-credit impaired loans | 90 days past due
Loans and Allowance for Loan Losses
Past due		275
Acquired non-credit impaired loans | Construction and land development
Loans and Allowance for Loan Losses
Total loans			53,302
Acquired non-credit impaired loans | Commercial non-owner occupied
Loans and Allowance for Loan Losses
Total loans			503,443
Acquired non-credit impaired loans | Commercial owner occupied real estate loan
Loans and Allowance for Loan Losses
Total loans			345,040
Acquired non-credit impaired loans | Consumer Owner Occupied Loans
Loans and Allowance for Loan Losses
Total loans			543,432
Acquired non-credit impaired loans | Home equity loans
Loans and Allowance for Loan Losses
Total loans			198,112
Acquired non-credit impaired loans | Commercial and industrial
Loans and Allowance for Loan Losses
Total loans			126,092
Acquired non-credit impaired loans | Other income producing property
Loans and Allowance for Loan Losses
Past due		4,735	1,300
Current		89,861	101,523
Non-Accruing		1,101	270
Total loans		95,697	103,093
Acquired non-credit impaired loans | Other income producing property | 30 days past due
Loans and Allowance for Loan Losses
Past due		378	1,008
Acquired non-credit impaired loans | Other income producing property | 60 days past due
Loans and Allowance for Loan Losses
Past due		4,309	292
Acquired non-credit impaired loans | Other income producing property | 90 days past due
Loans and Allowance for Loan Losses
Past due		48
Acquired non-credit impaired loans | Consumer
Loans and Allowance for Loan Losses
Total loans			93,089
Acquired non-credit impaired loans | Commercial loans
Loans and Allowance for Loan Losses
Total loans		985,780	1,130,970
Acquired non-credit impaired loans | Commercial loans | Construction and land development
Loans and Allowance for Loan Losses
Past due		112	323
Current		32,758	51,948
Non-Accruing		699	1,031
Total loans		33,569	53,302
Acquired non-credit impaired loans | Commercial loans | Construction and land development | 30 days past due
Loans and Allowance for Loan Losses
Past due		20	323
Acquired non-credit impaired loans | Commercial loans | Construction and land development | 90 days past due
Loans and Allowance for Loan Losses
Past due		92
Acquired non-credit impaired loans | Commercial loans | Commercial non-owner occupied
Loans and Allowance for Loan Losses
Past due		1,366	697
Current		445,682	502,480
Non-Accruing		393	266
Total loans		447,441	503,443
Acquired non-credit impaired loans | Commercial loans | Commercial non-owner occupied | 30 days past due
Loans and Allowance for Loan Losses
Past due		144	697
Acquired non-credit impaired loans | Commercial loans | Commercial non-owner occupied | 60 days past due
Loans and Allowance for Loan Losses
Past due		1,146
Acquired non-credit impaired loans | Commercial loans | Commercial non-owner occupied | 90 days past due
Loans and Allowance for Loan Losses
Past due		76
Acquired non-credit impaired loans | Commercial loans | Commercial owner occupied real estate loan
Loans and Allowance for Loan Losses
Past due		1,592	2,568
Current		304,698	341,539
Non-Accruing		903	933
Total loans		307,193	345,040
Acquired non-credit impaired loans | Commercial loans | Commercial owner occupied real estate loan | 30 days past due
Loans and Allowance for Loan Losses
Past due		890	2,400
Acquired non-credit impaired loans | Commercial loans | Commercial owner occupied real estate loan | 60 days past due
Loans and Allowance for Loan Losses
Past due		702	168
Acquired non-credit impaired loans | Commercial loans | Commercial and industrial
Loans and Allowance for Loan Losses
Past due		297	889
Current		100,861	124,511
Non-Accruing		722	692
Total loans		101,880	126,092
Acquired non-credit impaired loans | Commercial loans | Commercial and industrial | 30 days past due
Loans and Allowance for Loan Losses
Past due		93	857
Acquired non-credit impaired loans | Commercial loans | Commercial and industrial | 60 days past due
Loans and Allowance for Loan Losses
Past due		204	32
Acquired non-credit impaired loans | Commercial loans | Other income producing property
Loans and Allowance for Loan Losses
Total loans		95,697	103,093
Acquired non-credit impaired loans | Consumer
Loans and Allowance for Loan Losses
Total loans		774,647	834,633
Acquired non-credit impaired loans | Consumer | Real estate
Loans and Allowance for Loan Losses
Total loans		685,163	741,544
Acquired non-credit impaired loans | Consumer | Consumer Owner Occupied Loans
Loans and Allowance for Loan Losses
Past due		720	807
Current		493,361	540,886
Non-Accruing		2,350	1,739
Total loans		496,431	543,432
Acquired non-credit impaired loans | Consumer | Consumer Owner Occupied Loans | 30 days past due
Loans and Allowance for Loan Losses
Past due		637	807
Acquired non-credit impaired loans | Consumer | Consumer Owner Occupied Loans | 60 days past due
Loans and Allowance for Loan Losses
Past due		24
Acquired non-credit impaired loans | Consumer | Consumer Owner Occupied Loans | 90 days past due
Loans and Allowance for Loan Losses
Past due		59
Acquired non-credit impaired loans | Consumer | Home equity loans
Loans and Allowance for Loan Losses
Past due		287	545
Current		185,378	194,533
Non-Accruing		3,067	3,034
Total loans		188,732	198,112
Acquired non-credit impaired loans | Consumer | Home equity loans | 30 days past due
Loans and Allowance for Loan Losses
Past due		232	438
Acquired non-credit impaired loans | Consumer | Home equity loans | 60 days past due
Loans and Allowance for Loan Losses
Past due		55	107
Acquired non-credit impaired loans | Consumer | Consumer
Loans and Allowance for Loan Losses
Past due		555	479
Current		87,325	90,979
Non-Accruing		1,604	1,631
Total loans		89,484	93,089
Acquired non-credit impaired loans | Consumer | Consumer | 30 days past due
Loans and Allowance for Loan Losses
Past due		364	446
Acquired non-credit impaired loans | Consumer | Consumer | 60 days past due
Loans and Allowance for Loan Losses
Past due		191	33
Acquired credit impaired loans
Loans and Allowance for Loan Losses
Past due		17,460	14,183
Current		344,386	381,849
Total loans		361,846	396,032
Acquired credit impaired loans | 30 days past due
Loans and Allowance for Loan Losses
Past due		6,059	4,079
Acquired credit impaired loans | 60 days past due
Loans and Allowance for Loan Losses
Past due		2,169	1,580
Acquired credit impaired loans | 90 days past due
Loans and Allowance for Loan Losses
Past due		9,232	8,524
Acquired credit impaired loans | Construction and land development
Loans and Allowance for Loan Losses
Total loans			26,930
Acquired credit impaired loans | Commercial and industrial
Loans and Allowance for Loan Losses
Total loans			8,112
Acquired credit impaired loans | Consumer
Loans and Allowance for Loan Losses
Total loans			36,812
Acquired credit impaired loans | Commercial loans | Real estate
Loans and Allowance for Loan Losses
Past due		4,942	3,367
Current		125,996	145,767
Total loans		130,938	149,134
Acquired credit impaired loans | Commercial loans | Real estate | 30 days past due
Loans and Allowance for Loan Losses
Past due		2,283	444
Acquired credit impaired loans | Commercial loans | Real estate | 60 days past due
Loans and Allowance for Loan Losses
Past due			252
Acquired credit impaired loans | Commercial loans | Real estate | 90 days past due
Loans and Allowance for Loan Losses
Past due		2,659	2,671
Acquired credit impaired loans | Commercial loans | Construction and land development
Loans and Allowance for Loan Losses
Past due		393	349
Current		24,639	26,581
Total loans		25,032	26,930
Acquired credit impaired loans | Commercial loans | Construction and land development | 30 days past due
Loans and Allowance for Loan Losses
Past due			88
Acquired credit impaired loans | Commercial loans | Construction and land development | 90 days past due
Loans and Allowance for Loan Losses
Past due		393	261
Acquired credit impaired loans | Commercial loans | Commercial and industrial
Loans and Allowance for Loan Losses
Past due		1,103	359
Current		5,926	7,753
Total loans		7,029	8,112
Acquired credit impaired loans | Commercial loans | Commercial and industrial | 30 days past due
Loans and Allowance for Loan Losses
Past due		118	282
Acquired credit impaired loans | Commercial loans | Commercial and industrial | 60 days past due
Loans and Allowance for Loan Losses
Past due		910
Acquired credit impaired loans | Commercial loans | Commercial and industrial | 90 days past due
Loans and Allowance for Loan Losses
Past due		75	77
Acquired credit impaired loans | Consumer | Real estate
Loans and Allowance for Loan Losses
Past due		9,385	8,476
Current		153,974	166,568
Total loans		163,359	175,044
Acquired credit impaired loans | Consumer | Real estate | 30 days past due
Loans and Allowance for Loan Losses
Past due		2,838	2,317
Acquired credit impaired loans | Consumer | Real estate | 60 days past due
Loans and Allowance for Loan Losses
Past due		976	1,143
Acquired credit impaired loans | Consumer | Real estate | 90 days past due
Loans and Allowance for Loan Losses
Past due		5,571	5,016
Acquired credit impaired loans | Consumer | Consumer
Loans and Allowance for Loan Losses
Past due		1,637	1,632
Current		33,851	35,180
Total loans		35,488	36,812
Acquired credit impaired loans | Consumer | Consumer | 30 days past due
Loans and Allowance for Loan Losses
Past due		820	948
Acquired credit impaired loans | Consumer | Consumer | 60 days past due
Loans and Allowance for Loan Losses
Past due		283	185
Acquired credit impaired loans | Consumer | Consumer | 90 days past due
Loans and Allowance for Loan Losses
Past due		$ 534	$ 499