Loans - Summary of non-acquired loans (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Summary of Loans
Total loans		$ 11,375,104	$ 11,226,192
Less allowance for credit losses	$ (434,608)	(56,927)	(53,590)
Loans, net	$ 25,064,539	11,313,113	11,167,979
Construction and land development
Summary of Loans
Total loans		1,017,261	957,346
Consumer Owner Occupied Loans
Summary of Loans
Total loans		2,706,960	2,762,266
Other income producing property
Summary of Loans
Total loans		346,554	367,353
Commercial loans | Commercial non-owner occupied
Summary of Loans
Total loans		2,323,967	2,398,249
Commercial loans | Commercial non-owner occupied real estate
Summary of Loans
Total loans		3,341,228	3,355,595
Commercial loans | Commercial owner occupied real estate loan
Summary of Loans
Total loans		2,158,701	2,047,933
Commercial loans | Commercial and industrial
Summary of Loans
Total loans		1,386,327	1,271,464
Commercial loans | Other loans
Summary of Loans
Total loans		13,892	1,601
Consumer | Home equity loans
Summary of Loans
Total loans		758,020	778,234
Consumer | Real estate
Summary of Loans
Total loans		3,464,980	3,540,500
Consumer | Consumer
Summary of Loans
Total loans		663,422	641,746
Non-acquired loans
Summary of Loans
Total loans		9,252,831	8,621,327
Less allowance for credit losses		(56,927)	(53,590)
Loans, net		9,195,904	8,567,737
Non-acquired loans | Other income producing property
Summary of Loans
Total loans		218,617	214,203
Non-acquired loans | Commercial loans
Summary of Loans
Total loans		6,062,991	5,522,067
Non-acquired loans | Commercial loans | Construction and land development
Summary of Loans
Total loans		968,360	879,724
Non-acquired loans | Commercial loans | Commercial non-owner occupied
Summary of Loans
Total loans		1,811,138	1,723,640
Non-acquired loans | Commercial loans | Commercial non-owner occupied real estate
Summary of Loans
Total loans		2,779,498	2,603,364
Non-acquired loans | Commercial loans | Commercial owner occupied real estate loan
Summary of Loans
Total loans		1,784,017	1,589,987
Non-acquired loans | Commercial loans | Commercial and industrial
Summary of Loans
Total loans		1,280,859	1,114,513
Non-acquired loans | Commercial loans | Other loans
Summary of Loans
Total loans		13,892	1,601
Non-acquired loans | Consumer
Summary of Loans
Total loans		3,189,840	3,099,260
Non-acquired loans | Consumer | Consumer Owner Occupied Loans
Summary of Loans
Total loans		2,118,839	2,079,949
Non-acquired loans | Consumer | Home equity loans
Summary of Loans
Total loans		518,628	514,242
Non-acquired loans | Consumer | Real estate
Summary of Loans
Total loans		2,637,467	2,594,191
Non-acquired loans | Consumer | Consumer
Summary of Loans
Total loans		538,481	503,468
Non-acquired loans | Consumer | Other loans
Summary of Loans
Total loans		$ 13,892	$ 1,601