Loans - Aging analysis of past due loans (Details) $ in Thousands	Mar. 31, 2020 USD ($)
Loans and Allowance for Loan Losses
Past due	$ 49,320
Current	11,457,570
Total loans - ASU 2016-13	11,506,890
Greater than 90 Days Accruing	362
30 days past due
Loans and Allowance for Loan Losses
Past due	23,193
60 days past due
Loans and Allowance for Loan Losses
Past due	7,317
90 days past due
Loans and Allowance for Loan Losses
Past due	18,810
Construction and land development
Loans and Allowance for Loan Losses
Past due	2,131
Current	1,103,177
Total loans - ASU 2016-13	1,105,308
Construction and land development | 30 days past due
Loans and Allowance for Loan Losses
Past due	1,700
Construction and land development | 60 days past due
Loans and Allowance for Loan Losses
Past due	67
Construction and land development | 90 days past due
Loans and Allowance for Loan Losses
Past due	364
Consumer Owner Occupied Loans
Loans and Allowance for Loan Losses
Past due	10,922
Current	2,654,483
Total loans - ASU 2016-13	2,665,405
Consumer Owner Occupied Loans | 30 days past due
Loans and Allowance for Loan Losses
Past due	6,047
Consumer Owner Occupied Loans | 60 days past due
Loans and Allowance for Loan Losses
Past due	467
Consumer Owner Occupied Loans | 90 days past due
Loans and Allowance for Loan Losses
Past due	4,408
Other income producing property
Loans and Allowance for Loan Losses
Past due	3,188
Current	324,508
Total loans - ASU 2016-13	327,696
Greater than 90 Days Accruing	74
Other income producing property | 30 days past due
Loans and Allowance for Loan Losses
Past due	1,338
Other income producing property | 60 days past due
Loans and Allowance for Loan Losses
Past due	143
Other income producing property | 90 days past due
Loans and Allowance for Loan Losses
Past due	1,707
Commercial loans
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	7,042,466
Commercial loans | Construction and land development
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	753,964
Commercial loans | Commercial non-owner occupied
Loans and Allowance for Loan Losses
Past due	3,670
Current	2,367,701
Total loans - ASU 2016-13	2,371,371
Commercial loans | Commercial non-owner occupied | 30 days past due
Loans and Allowance for Loan Losses
Past due	1,445
Commercial loans | Commercial non-owner occupied | 60 days past due
Loans and Allowance for Loan Losses
Past due	407
Commercial loans | Commercial non-owner occupied | 90 days past due
Loans and Allowance for Loan Losses
Past due	1,818
Commercial loans | Commercial owner occupied real estate loan
Loans and Allowance for Loan Losses
Past due	10,930
Current	2,166,808
Total loans - ASU 2016-13	2,177,738
Greater than 90 Days Accruing	119
Commercial loans | Commercial owner occupied real estate loan | 30 days past due
Loans and Allowance for Loan Losses
Past due	5,606
Commercial loans | Commercial owner occupied real estate loan | 60 days past due
Loans and Allowance for Loan Losses
Past due	156
Commercial loans | Commercial owner occupied real estate loan | 90 days past due
Loans and Allowance for Loan Losses
Past due	5,168
Commercial loans | Consumer Owner Occupied Loans
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	38,765
Commercial loans | Commercial and industrial
Loans and Allowance for Loan Losses
Past due	5,402
Current	1,413,019
Total loans - ASU 2016-13	1,418,421
Greater than 90 Days Accruing	167
Commercial loans | Commercial and industrial | 30 days past due
Loans and Allowance for Loan Losses
Past due	2,128
Commercial loans | Commercial and industrial | 60 days past due
Loans and Allowance for Loan Losses
Past due	2,220
Commercial loans | Commercial and industrial | 90 days past due
Loans and Allowance for Loan Losses
Past due	1,054
Commercial loans | Other income producing property
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	274,529
Commercial loans | Other loans
Loans and Allowance for Loan Losses
Current	7,678
Total loans - ASU 2016-13	7,678
Consumer
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	4,464,424
Consumer | 30 days past due
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	10,570
Consumer | 60 days past due
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	4,322
Consumer | 90 days past due
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	8,601
Consumer | Construction and land development
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	351,344
Consumer | Construction and land development | 30 days past due
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	266
Consumer | Construction and land development | 90 days past due
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	127
Consumer | Consumer Owner Occupied Loans
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	2,626,640
Consumer | Consumer Owner Occupied Loans | 30 days past due
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	5,789
Consumer | Consumer Owner Occupied Loans | 60 days past due
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	468
Consumer | Consumer Owner Occupied Loans | 90 days past due
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	4,184
Consumer | Home equity loans
Loans and Allowance for Loan Losses
Past due	7,613
Current	750,869
Total loans - ASU 2016-13	758,482
Consumer | Home equity loans | 30 days past due
Loans and Allowance for Loan Losses
Past due	2,359
Total loans - ASU 2016-13	2,359
Consumer | Home equity loans | 60 days past due
Loans and Allowance for Loan Losses
Past due	2,788
Total loans - ASU 2016-13	2,788
Consumer | Home equity loans | 90 days past due
Loans and Allowance for Loan Losses
Past due	2,466
Total loans - ASU 2016-13	2,466
Consumer | Other income producing property
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	53,167
Consumer | Other income producing property | 30 days past due
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	105
Consumer | Other income producing property | 90 days past due
Loans and Allowance for Loan Losses
Total loans - ASU 2016-13	1
Consumer | Consumer
Loans and Allowance for Loan Losses
Past due	5,464
Current	669,327
Total loans - ASU 2016-13	674,791
Greater than 90 Days Accruing	2
Consumer | Consumer | 30 days past due
Loans and Allowance for Loan Losses
Past due	2,570
Total loans - ASU 2016-13	2,051
Consumer | Consumer | 60 days past due
Loans and Allowance for Loan Losses
Past due	1,069
Total loans - ASU 2016-13	1,066
Consumer | Consumer | 90 days past due
Loans and Allowance for Loan Losses
Past due	1,825
Total loans - ASU 2016-13	$ 1,823