Loans - Aging analysis of past due loans (Details) $ in Thousands	Jun. 30, 2020 USD ($)
Loans and Allowance for Loan Losses
Past due	$ 41,692
Current	25,335,645
Non-Accruing	121,810
Total loans - ASU 2016-13	25,499,147
Greater than 90 Days Accruing	1,471
30 days past due
Loans and Allowance for Loan Losses
Past due	27,159
60 days past due
Loans and Allowance for Loan Losses
Past due	13,062
90 days past due
Loans and Allowance for Loan Losses
Past due	1,471
Construction and land development
Loans and Allowance for Loan Losses
Past due	2,444
Current	1,993,651
Non-Accruing	2,967
Total loans - ASU 2016-13	1,999,062
Construction and land development | 30 days past due
Loans and Allowance for Loan Losses
Past due	1,516
Construction and land development | 60 days past due
Loans and Allowance for Loan Losses
Past due	928
Consumer Owner Occupied Loans
Loans and Allowance for Loan Losses
Past due	11,969
Current	4,371,397
Non-Accruing	37,881
Total loans - ASU 2016-13	4,421,247
Greater than 90 Days Accruing	310
Consumer Owner Occupied Loans | 30 days past due
Loans and Allowance for Loan Losses
Past due	6,982
Consumer Owner Occupied Loans | 60 days past due
Loans and Allowance for Loan Losses
Past due	4,677
Consumer Owner Occupied Loans | 90 days past due
Loans and Allowance for Loan Losses
Past due	310
Other income producing property
Loans and Allowance for Loan Losses
Past due	1,360
Current	640,932
Non-Accruing	7,945
Total loans - ASU 2016-13	650,237
Greater than 90 Days Accruing	38
Other income producing property | 30 days past due
Loans and Allowance for Loan Losses
Past due	1,047
Other income producing property | 60 days past due
Loans and Allowance for Loan Losses
Past due	275
Other income producing property | 90 days past due
Loans and Allowance for Loan Losses
Past due	38
Commercial loans
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	18,075,732
Commercial loans | Construction and land development
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	1,305,510
Commercial loans | Commercial non-owner occupied
Loans and Allowance for Loan Losses
Past due	1,777
Current	6,009,897
Non-Accruing	9,643
Total loans - ASU 2016-13	6,021,317
Commercial loans | Commercial non-owner occupied | 30 days past due
Loans and Allowance for Loan Losses
Past due	1,027
Commercial loans | Commercial non-owner occupied | 60 days past due
Loans and Allowance for Loan Losses
Past due	750
Commercial loans | Commercial owner occupied real estate loan
Loans and Allowance for Loan Losses
Past due	3,904
Current	4,722,026
Non-Accruing	36,590
Total loans - ASU 2016-13	4,762,520
Greater than 90 Days Accruing	16
Commercial loans | Commercial owner occupied real estate loan | 30 days past due
Loans and Allowance for Loan Losses
Past due	3,477
Commercial loans | Commercial owner occupied real estate loan | 60 days past due
Loans and Allowance for Loan Losses
Past due	411
Commercial loans | Commercial owner occupied real estate loan | 90 days past due
Loans and Allowance for Loan Losses
Past due	16
Commercial loans | Consumer Owner Occupied Loans
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	38,387
Commercial loans | Commercial and industrial
Loans and Allowance for Loan Losses
Past due	13,880
Current	5,320,273
Non-Accruing	7,210
Total loans - ASU 2016-13	5,341,363
Greater than 90 Days Accruing	1,107
Commercial loans | Commercial and industrial | 30 days past due
Loans and Allowance for Loan Losses
Past due	9,070
Commercial loans | Commercial and industrial | 60 days past due
Loans and Allowance for Loan Losses
Past due	3,703
Commercial loans | Commercial and industrial | 90 days past due
Loans and Allowance for Loan Losses
Past due	1,107
Commercial loans | Other income producing property
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	598,263
Commercial loans | Other loans
Loans and Allowance for Loan Losses
Past due	25
Current	8,347
Total loans - ASU 2016-13	8,372
Commercial loans | Other loans | 30 days past due
Loans and Allowance for Loan Losses
Past due	16
Commercial loans | Other loans | 60 days past due
Loans and Allowance for Loan Losses
Past due	9
Consumer
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	7,423,415
Consumer | 30 days past due
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	12,225
Consumer | 60 days past due
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	8,616
Consumer | 90 days past due
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	23,118
Consumer | Construction and land development
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	693,552
Consumer | Construction and land development | 30 days past due
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	24
Consumer | Construction and land development | 60 days past due
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	275
Consumer | Construction and land development | 90 days past due
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	274
Consumer | Consumer Owner Occupied Loans
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	4,382,860
Consumer | Consumer Owner Occupied Loans | 30 days past due
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	7,482
Consumer | Consumer Owner Occupied Loans | 60 days past due
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	5,610
Consumer | Consumer Owner Occupied Loans | 90 days past due
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	12,196
Consumer | Home equity loans
Loans and Allowance for Loan Losses
Past due	3,914
Current	1,361,489
Non-Accruing	13,003
Total loans - ASU 2016-13	1,378,406
Consumer | Home equity loans | 30 days past due
Loans and Allowance for Loan Losses
Past due	2,500
Total loans - ASU 2016-13	2,920
Consumer | Home equity loans | 60 days past due
Loans and Allowance for Loan Losses
Past due	1,414
Total loans - ASU 2016-13	1,453
Consumer | Home equity loans | 90 days past due
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	7,932
Consumer | Other income producing property
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	51,974
Consumer | Other income producing property | 30 days past due
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	14
Consumer | Consumer
Loans and Allowance for Loan Losses
Past due	2,419
Current	907,633
Non-Accruing	6,571
Total loans - ASU 2016-13	916,623
Consumer | Consumer | 30 days past due
Loans and Allowance for Loan Losses
Past due	1,524
Total loans - ASU 2016-13	1,785
Consumer | Consumer | 60 days past due
Loans and Allowance for Loan Losses
Past due	895
Total loans - ASU 2016-13	1,278
Consumer | Consumer | 90 days past due
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	$ 2,716