Loans - Summary of non-acquired loans (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Summary of Loans
Total loans		$ 11,375,104	$ 11,146,122
Less allowance for loan losses	$ (144,785)	(61,991)	(56,522)
Loans, net	11,362,105	11,313,113	11,089,600
Construction and land development
Summary of Loans
Total loans		1,017,261	946,503
Consumer Owner Occupied Loans
Summary of Loans
Total loans		2,706,960	2,731,499
Other income producing property
Summary of Loans
Total loans		346,554	380,177
Commercial loans | Commercial non-owner occupied
Summary of Loans
Total loans		2,323,967	2,329,449
Commercial loans | Commercial non-owner occupied real estate
Summary of Loans
Total loans		3,341,228	3,275,952
Commercial loans | Commercial owner occupied real estate loan
Summary of Loans
Total loans		2,158,701	2,086,662
Commercial loans | Commercial and industrial
Summary of Loans
Total loans		1,386,327	1,251,719
Commercial loans | Other loans
Summary of Loans
Total loans		13,892	18,224
Consumer | Home equity loans
Summary of Loans
Total loans		758,020	791,658
Consumer | Real estate
Summary of Loans
Total loans		3,464,980	3,523,157
Consumer | Consumer
Summary of Loans
Total loans		663,422	610,231
Non-acquired loans
Summary of Loans
Total loans		9,252,831	8,310,613
Less allowance for loan losses	$ (144,785)	(56,927)	(52,008)
Loans, net		9,195,904	8,258,605
Non-acquired loans | Other income producing property
Summary of Loans
Total loans		218,617	214,235
Non-acquired loans | Commercial loans
Summary of Loans
Total loans		6,062,991	5,313,632
Non-acquired loans | Commercial loans | Construction and land development
Summary of Loans
Total loans		968,360	810,551
Non-acquired loans | Commercial loans | Commercial non-owner occupied
Summary of Loans
Total loans		1,811,138	1,615,416
Non-acquired loans | Commercial loans | Commercial non-owner occupied real estate
Summary of Loans
Total loans		2,779,498	2,425,967
Non-acquired loans | Commercial loans | Commercial owner occupied real estate loan
Summary of Loans
Total loans		1,784,017	1,601,360
Non-acquired loans | Commercial loans | Commercial and industrial
Summary of Loans
Total loans		1,280,859	1,072,070
Non-acquired loans | Commercial loans | Other loans
Summary of Loans
Total loans		13,892	18,224
Non-acquired loans | Consumer
Summary of Loans
Total loans		3,189,840	2,996,981
Non-acquired loans | Consumer | Consumer Owner Occupied Loans
Summary of Loans
Total loans		2,118,839	2,005,314
Non-acquired loans | Consumer | Home equity loans
Summary of Loans
Total loans		518,628	508,326
Non-acquired loans | Consumer | Real estate
Summary of Loans
Total loans		2,637,467	2,513,640
Non-acquired loans | Consumer | Consumer
Summary of Loans
Total loans		538,481	465,117
Non-acquired loans | Consumer | Other loans
Summary of Loans
Total loans		$ 13,892	$ 18,224