Loans - Summary of loans (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019
Summary of Loans
Total loans - ASU 2016-13	$ 25,237,815
Total loans		$ 11,375,104	$ 11,290,147
Less allowance for credit losses	(440,159)	(56,927)	(54,937)
Loans, net	24,797,656	11,313,113	11,229,892
Deferred costs	50,500
Unamortized Discounts	110,400
Accrued interest receivable (AIR)	97,800
Acquired credit impaired loans
Summary of Loans
Total loans		361,846	396,032
Less allowance for credit losses		(5,064)	(5,318)
Loans, net		356,782	390,714
Previous Accounting Guidance [Member]
Summary of Loans
Less allowance for credit losses		(61,991)	(60,255)
Construction and land development
Summary of Loans
Total loans - ASU 2016-13	1,840,111
Total loans		1,017,261	1,025,387
Construction and land development | Acquired credit impaired loans
Summary of Loans
Total loans			26,930
Consumer Owner Occupied Loans
Summary of Loans
Total loans - ASU 2016-13	4,311,186
Total loans		2,706,960	2,760,126
Commercial and industrial | Acquired credit impaired loans
Summary of Loans
Total loans			8,112
Other income producing property
Summary of Loans
Total loans - ASU 2016-13	629,497
Total loans		346,554	361,879
Consumer | Acquired credit impaired loans
Summary of Loans
Total loans			36,812
Other loans
Summary of Loans
Total loans - ASU 2016-13	7,540
Total loans		13,892	1,457
Commercial loans
Summary of Loans
Total loans - ASU 2016-13	17,982,997
Commercial loans | Construction and land development
Summary of Loans
Total loans - ASU 2016-13	1,157,423
Commercial loans | Construction and land development | Acquired credit impaired loans
Summary of Loans
Total loans		25,032	26,930
Commercial loans | Commercial non-owner occupied
Summary of Loans
Total loans - ASU 2016-13	5,936,372
Total loans		2,323,967	2,357,730
Commercial loans | Commercial non-owner occupied real estate
Summary of Loans
Total loans - ASU 2016-13	4,846,020
Total loans		2,158,701	2,093,795
Commercial loans | Consumer Owner Occupied Loans
Summary of Loans
Total loans - ASU 2016-13	34,890
Commercial loans | Real estate | Acquired credit impaired loans
Summary of Loans
Total loans		130,938	149,134
Commercial loans | Commercial owner occupied real estate loan
Summary of Loans
Total loans - ASU 2016-13	4,846,020
Commercial loans | Commercial and industrial
Summary of Loans
Total loans - ASU 2016-13	5,419,120
Total loans		1,386,327	1,261,527
Commercial loans | Commercial and industrial | Acquired credit impaired loans
Summary of Loans
Total loans		7,029	8,112
Commercial loans | Other income producing property
Summary of Loans
Total loans - ASU 2016-13	581,632
Commercial loans | Other loans
Summary of Loans
Total loans - ASU 2016-13	7,540
Consumer
Summary of Loans
Total loans - ASU 2016-13	7,254,818
Consumer | Construction and land development
Summary of Loans
Total loans - ASU 2016-13	682,688
Consumer | Consumer Owner Occupied Loans
Summary of Loans
Total loans - ASU 2016-13	4,276,296
Consumer | Home equity loans
Summary of Loans
Total loans - ASU 2016-13	1,347,798
Total loans		758,020	773,363
Consumer | Real estate | Acquired credit impaired loans
Summary of Loans
Total loans		163,359	175,044
Consumer | Other income producing property
Summary of Loans
Total loans - ASU 2016-13	47,865
Consumer | Consumer
Summary of Loans
Total loans - ASU 2016-13	$ 900,171
Total loans		663,422	654,883
Consumer | Consumer | Acquired credit impaired loans
Summary of Loans
Total loans		$ 35,488	$ 36,812