Purchased Loans - Aging of Past Due and Nonaccrual Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	$ 10,933,647	$ 9,689,638
Commercial, financial, agriculture
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	2,536,984	1,367,972
Real estate - construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	858,104	826,483
Real estate - 1-4 family mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	2,698,308	2,866,613
Real estate - commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	4,554,852	4,244,265
Installment loans to individuals
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	209,537	384,305
Purchased
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,514,107	2,101,664
Purchased | Accruing Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current Loans	1,474,138	2,075,422
Loans, net of unearned income	1,483,056	2,094,626
Purchased | Accruing Loans | 30-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	8,651	14,887
Purchased | Accruing Loans | 90 Days or More Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	267	4,317
Purchased | Nonaccruing Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current Loans	15,412	2,250
Loans, net of unearned income	31,051	7,038
Purchased | Nonaccruing Loans | 30-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	8,671	606
Purchased | Nonaccruing Loans | 90 Days or More Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	6,968	4,182
Purchased | Commercial, financial, agriculture
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	176,513	315,619
Purchased | Commercial, financial, agriculture | Accruing Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current loans	163,658	311,218
Loans, net of unearned income	164,577	314,105
Purchased | Commercial, financial, agriculture | Accruing Loans | 30-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	818	1,889
Purchased | Commercial, financial, agriculture | Accruing Loans | 90 Days or More Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	101	998
Purchased | Commercial, financial, agriculture | Nonaccruing Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current loans	9,838	268
Loans, net of unearned income	11,936	1,514
Purchased | Commercial, financial, agriculture | Nonaccruing Loans | 30-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	74	0
Purchased | Commercial, financial, agriculture | Nonaccruing Loans | 90 Days or More Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	2,024	1,246
Purchased | Real estate - construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	30,952	51,582
Purchased | Real estate - construction | Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	2,859	16,407
Purchased | Real estate - construction | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	28,093	35,175
Purchased | Real estate - construction | Accruing Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current loans	30,952	51,263
Loans, net of unearned income	30,952	51,582
Purchased | Real estate - construction | Accruing Loans | Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current loans	2,859
Loans, net of unearned income	2,859
Purchased | Real estate - construction | Accruing Loans | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current loans	28,093
Loans, net of unearned income	28,093
Purchased | Real estate - construction | Accruing Loans | 30-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	0	319
Purchased | Real estate - construction | Accruing Loans | 30-89 Days Past Due | Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	0
Purchased | Real estate - construction | Accruing Loans | 30-89 Days Past Due | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	0
Purchased | Real estate - construction | Accruing Loans | 90 Days or More Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	0	0
Purchased | Real estate - construction | Accruing Loans | 90 Days or More Past Due | Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	0
Purchased | Real estate - construction | Accruing Loans | 90 Days or More Past Due | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	0
Purchased | Real estate - construction | Nonaccruing Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current loans	0	0
Loans, net of unearned income	0	0
Purchased | Real estate - construction | Nonaccruing Loans | Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current loans	0
Loans, net of unearned income	0
Purchased | Real estate - construction | Nonaccruing Loans | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current loans	0
Loans, net of unearned income	0
Purchased | Real estate - construction | Nonaccruing Loans | 30-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	0	0
Purchased | Real estate - construction | Nonaccruing Loans | 30-89 Days Past Due | Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	0
Purchased | Real estate - construction | Nonaccruing Loans | 30-89 Days Past Due | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	0
Purchased | Real estate - construction | Nonaccruing Loans | 90 Days or More Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	0	0
Purchased | Real estate - construction | Nonaccruing Loans | 90 Days or More Past Due | Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	0
Purchased | Real estate - construction | Nonaccruing Loans | 90 Days or More Past Due | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	0
Purchased | Real estate - 1-4 family mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	341,744	516,487
Purchased | Real estate - 1-4 family mortgage | Primary
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	214,770	332,729
Purchased | Real estate - 1-4 family mortgage | Home Equity Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	80,392	117,275
Purchased | Real estate - 1-4 family mortgage | Rental / Investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	31,928	43,169
Purchased | Real estate - 1-4 family mortgage | Land Development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	14,654	23,314
Purchased | Real estate - 1-4 family mortgage | Accruing Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current loans	330,536	503,826
Loans, net of unearned income	333,644	511,586
Purchased | Real estate - 1-4 family mortgage | Accruing Loans | Primary
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current loans	206,635
Loans, net of unearned income	209,103
Purchased | Real estate - 1-4 family mortgage | Accruing Loans | Home Equity Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current loans	78,739
Loans, net of unearned income	79,076
Purchased | Real estate - 1-4 family mortgage | Accruing Loans | Rental / Investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current loans	30,931
Loans, net of unearned income	31,125
Purchased | Real estate - 1-4 family mortgage | Accruing Loans | Land Development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current loans	14,231
Loans, net of unearned income	14,340
Purchased | Real estate - 1-4 family mortgage | Accruing Loans | 30-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	2,977	5,516
Purchased | Real estate - 1-4 family mortgage | Accruing Loans | 30-89 Days Past Due | Primary
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	2,394
Purchased | Real estate - 1-4 family mortgage | Accruing Loans | 30-89 Days Past Due | Home Equity Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	294
Purchased | Real estate - 1-4 family mortgage | Accruing Loans | 30-89 Days Past Due | Rental / Investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	180
Purchased | Real estate - 1-4 family mortgage | Accruing Loans | 30-89 Days Past Due | Land Development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	109
Purchased | Real estate - 1-4 family mortgage | Accruing Loans | 90 Days or More Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	131	2,244
Purchased | Real estate - 1-4 family mortgage | Accruing Loans | 90 Days or More Past Due | Primary
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	74
Purchased | Real estate - 1-4 family mortgage | Accruing Loans | 90 Days or More Past Due | Home Equity Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	43
Purchased | Real estate - 1-4 family mortgage | Accruing Loans | 90 Days or More Past Due | Rental / Investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	14
Purchased | Real estate - 1-4 family mortgage | Accruing Loans | 90 Days or More Past Due | Land Development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	0
Purchased | Real estate - 1-4 family mortgage | Nonaccruing Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current loans	3,212	1,534
Loans, net of unearned income	8,100	4,901
Purchased | Real estate - 1-4 family mortgage | Nonaccruing Loans | Primary
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current loans	2,181
Loans, net of unearned income	5,667
Purchased | Real estate - 1-4 family mortgage | Nonaccruing Loans | Home Equity Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current loans	638
Loans, net of unearned income	1,316
Purchased | Real estate - 1-4 family mortgage | Nonaccruing Loans | Rental / Investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current loans	79
Loans, net of unearned income	803
Purchased | Real estate - 1-4 family mortgage | Nonaccruing Loans | Land Development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current loans	314
Loans, net of unearned income	314
Purchased | Real estate - 1-4 family mortgage | Nonaccruing Loans | 30-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	691	605
Purchased | Real estate - 1-4 family mortgage | Nonaccruing Loans | 30-89 Days Past Due | Primary
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	687
Purchased | Real estate - 1-4 family mortgage | Nonaccruing Loans | 30-89 Days Past Due | Home Equity Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	4
Purchased | Real estate - 1-4 family mortgage | Nonaccruing Loans | 30-89 Days Past Due | Rental / Investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	0
Purchased | Real estate - 1-4 family mortgage | Nonaccruing Loans | 30-89 Days Past Due | Land Development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	0
Purchased | Real estate - 1-4 family mortgage | Nonaccruing Loans | 90 Days or More Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	4,197	2,762
Purchased | Real estate - 1-4 family mortgage | Nonaccruing Loans | 90 Days or More Past Due | Primary
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	2,799
Purchased | Real estate - 1-4 family mortgage | Nonaccruing Loans | 90 Days or More Past Due | Home Equity Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	674
Purchased | Real estate - 1-4 family mortgage | Nonaccruing Loans | 90 Days or More Past Due | Rental / Investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	724
Purchased | Real estate - 1-4 family mortgage | Nonaccruing Loans | 90 Days or More Past Due | Land Development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	0
Purchased | Real estate - commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	905,223	1,115,389
Purchased | Real estate - commercial mortgage | Land Development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	29,454
Purchased | Real estate - commercial mortgage | Owner Occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	323,041	428,077
Purchased | Real estate - commercial mortgage | Non-owner Occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	552,728	647,308
Purchased | Real estate - commercial mortgage | Accruing Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current loans	891,653	1,110,570
Loans, net of unearned income	894,483	1,114,946
Purchased | Real estate - commercial mortgage | Accruing Loans | Land Development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current loans	28,962
Loans, net of unearned income	29,074
Purchased | Real estate - commercial mortgage | Accruing Loans | Owner Occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current loans	317,997
Loans, net of unearned income	320,508
Purchased | Real estate - commercial mortgage | Accruing Loans | Non-owner Occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current loans	544,694
Loans, net of unearned income	544,901
Purchased | Real estate - commercial mortgage | Accruing Loans | 30-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	2,830	3,454
Purchased | Real estate - commercial mortgage | Accruing Loans | 30-89 Days Past Due | Land Development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	112
Purchased | Real estate - commercial mortgage | Accruing Loans | 30-89 Days Past Due | Owner Occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	2,511
Purchased | Real estate - commercial mortgage | Accruing Loans | 30-89 Days Past Due | Non-owner Occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	207
Purchased | Real estate - commercial mortgage | Accruing Loans | 90 Days or More Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	0	922
Purchased | Real estate - commercial mortgage | Accruing Loans | 90 Days or More Past Due | Land Development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	0
Purchased | Real estate - commercial mortgage | Accruing Loans | 90 Days or More Past Due | Owner Occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	0
Purchased | Real estate - commercial mortgage | Accruing Loans | 90 Days or More Past Due | Non-owner Occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	0
Purchased | Real estate - commercial mortgage | Nonaccruing Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current loans	2,254	320
Loans, net of unearned income	10,740	443
Purchased | Real estate - commercial mortgage | Nonaccruing Loans | Land Development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current loans	216
Loans, net of unearned income	380
Purchased | Real estate - commercial mortgage | Nonaccruing Loans | Owner Occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current loans	1,893
Loans, net of unearned income	2,533
Purchased | Real estate - commercial mortgage | Nonaccruing Loans | Non-owner Occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current loans	145
Loans, net of unearned income	7,827
Purchased | Real estate - commercial mortgage | Nonaccruing Loans | 30-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	7,875	0
Purchased | Real estate - commercial mortgage | Nonaccruing Loans | 30-89 Days Past Due | Land Development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	0
Purchased | Real estate - commercial mortgage | Nonaccruing Loans | 30-89 Days Past Due | Owner Occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	193
Purchased | Real estate - commercial mortgage | Nonaccruing Loans | 30-89 Days Past Due | Non-owner Occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	7,682
Purchased | Real estate - commercial mortgage | Nonaccruing Loans | 90 Days or More Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	611	123
Purchased | Real estate - commercial mortgage | Nonaccruing Loans | 90 Days or More Past Due | Land Development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	164
Purchased | Real estate - commercial mortgage | Nonaccruing Loans | 90 Days or More Past Due | Owner Occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	447
Purchased | Real estate - commercial mortgage | Nonaccruing Loans | 90 Days or More Past Due | Non-owner Occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	0
Purchased | Installment loans to individuals
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	59,675	102,587
Purchased | Installment loans to individuals | Accruing Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current loans	57,339	98,545
Loans, net of unearned income	59,400	102,407
Purchased | Installment loans to individuals | Accruing Loans | 30-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	2,026	3,709
Purchased | Installment loans to individuals | Accruing Loans | 90 Days or More Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	35	153
Purchased | Installment loans to individuals | Nonaccruing Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current loans	108	128
Loans, net of unearned income	275	180
Purchased | Installment loans to individuals | Nonaccruing Loans | 30-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	31	1
Purchased | Installment loans to individuals | Nonaccruing Loans | 90 Days or More Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due, gross	$ 136	$ 51