Loans - Summary of non-acquired loans (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019
Summary of Loans
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
Construction and land development
Summary of Loans
Total loans		1,017,261	1,025,387
Consumer Owner Occupied Loans
Summary of Loans
Total loans		2,706,960	2,760,126
Other income producing property
Summary of Loans
Total loans		346,554	361,879
Other loans
Summary of Loans
Total loans		13,892	1,457
Commercial loans | Commercial non-owner occupied
Summary of Loans
Total loans		2,323,967	2,357,730
Commercial loans | Commercial non-owner occupied real estate
Summary of Loans
Total loans		2,158,701	2,093,795
Commercial loans | Commercial and industrial
Summary of Loans
Total loans		1,386,327	1,261,527
Consumer | Home equity loans
Summary of Loans
Total loans		758,020	773,363
Consumer | Consumer
Summary of Loans
Total loans		663,422	654,883
Non-acquired loans
Summary of Loans
Total loans		9,252,831	8,928,512
Less allowance for credit losses		(56,927)	(54,937)
Loans, net		9,195,904	8,873,575
Non-acquired loans | Construction and land development
Summary of Loans
Total loans			955,318
Non-acquired loans | Commercial non-owner occupied
Summary of Loans
Total loans			1,777,327
Non-acquired loans | Consumer Owner Occupied Loans
Summary of Loans
Total loans			2,118,127
Non-acquired loans | Home equity loans
Summary of Loans
Total loans			521,744
Non-acquired loans | Commercial owner occupied real estate loan
Summary of Loans
Total loans			1,677,695
Non-acquired loans | Commercial and industrial
Summary of Loans
Total loans			1,130,847
Non-acquired loans | Other income producing property
Summary of Loans
Total loans		218,617	220,957
Non-acquired loans | Consumer
Summary of Loans
Total loans			525,040
Non-acquired loans | Other loans
Summary of Loans
Total loans		13,892	1,457
Non-acquired loans | Commercial loans
Summary of Loans
Total loans		6,062,991	5,762,144
Non-acquired loans | Commercial loans | Construction and land development
Summary of Loans
Total loans		968,360	955,318
Non-acquired loans | Commercial loans | Commercial non-owner occupied
Summary of Loans
Total loans		1,811,138	1,777,327
Non-acquired loans | Commercial loans | Commercial non-owner occupied real estate
Summary of Loans
Total loans		2,779,498	2,732,645
Non-acquired loans | Commercial loans | Real estate
Summary of Loans
Total loans		968,360
Non-acquired loans | Commercial loans | Commercial owner occupied real estate loan
Summary of Loans
Total loans		1,784,017	1,677,695
Non-acquired loans | Commercial loans | Commercial and industrial
Summary of Loans
Total loans		1,280,859	1,130,847
Non-acquired loans | Commercial loans | Other income producing property
Summary of Loans
Total loans		218,617	220,957
Non-acquired loans | Consumer
Summary of Loans
Total loans		3,189,840	3,166,368
Non-acquired loans | Consumer | Consumer Owner Occupied Loans
Summary of Loans
Total loans		2,118,839	2,118,127
Non-acquired loans | Consumer | Home equity loans
Summary of Loans
Total loans		518,628	521,744
Non-acquired loans | Consumer | Real estate
Summary of Loans
Total loans		2,637,467	2,639,871
Non-acquired loans | Consumer | Consumer
Summary of Loans
Total loans		538,481	525,040
Non-acquired loans | Consumer | Other loans
Summary of Loans
Total loans		$ 13,892	$ 1,457