Loans and Leases - Age Analysis of Past Due Loans and Leases (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	$ 4,456,582	$ 4,460,111
Accruing loans and leases	5,293,809	5,275,149
Total nonaccrual loans and lease	33,504	31,692
Loans and leases held for investment	5,327,313	5,306,841	$ 4,951,809
Financial Asset, 30 to 59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	12,969	16,173
Financial Asset, 60 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	2,785	2,218
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	750	1,392
Financial Asset Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	16,504	19,783
Financial Asset Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	5,277,305	5,255,366
Commercial Financial And Agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	920,621	892,665
Accruing loans and leases	919,375	889,838
Total nonaccrual loans and lease	1,246	2,827
Loans and leases held for investment	920,621	892,665	822,733
Commercial Financial And Agricultural [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	629	1,104
Commercial Financial And Agricultural [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	599	279
Commercial Financial And Agricultural [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	476	50
Commercial Financial And Agricultural [Member] | Financial Asset Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	1,704	1,433
Commercial Financial And Agricultural [Member] | Financial Asset Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	917,671	888,405
Paycheck Protection Program Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	252,849	483,773
Accruing loans and leases	252,849	483,773
Total nonaccrual loans and lease	0	0
Loans and leases held for investment	252,849	483,773	498,978
Paycheck Protection Program Loans | Financial Asset, 30 to 59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	517	0
Paycheck Protection Program Loans | Financial Asset, 60 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	0	0
Paycheck Protection Program Loans | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	0	0
Paycheck Protection Program Loans | Financial Asset Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	517	0
Paycheck Protection Program Loans | Financial Asset Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	252,332	483,773
Real-Estate Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	2,600,919	2,458,872
Accruing loans and leases	2,574,655	2,436,133
Total nonaccrual loans and lease	26,264	22,739
Loans and leases held for investment	2,600,919	2,458,872	2,222,490
Real-Estate Commercial [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	7,734	3,230
Real-Estate Commercial [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	0	859
Real-Estate Commercial [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	137	945
Real-Estate Commercial [Member] | Financial Asset Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	7,871	5,034
Real-Estate Commercial [Member] | Financial Asset Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	2,566,784	2,431,099
Real-Estate Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	274,529	243,355
Accruing loans and leases	274,529	243,355
Total nonaccrual loans and lease	0	0
Loans and leases held for investment	274,529	243,355	212,534
Real-Estate Construction [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	153	361
Real-Estate Construction [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	0	0
Real-Estate Construction [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	0	0
Real-Estate Construction [Member] | Financial Asset Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	153	361
Real-Estate Construction [Member] | Financial Asset Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	274,376	242,994
Real Estate Residential Secured For Business Purpose [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	407,664	381,446
Accruing loans and leases	404,619	378,660
Total nonaccrual loans and lease	3,045	2,786
Loans and leases held for investment	407,664	381,446	376,050
Real Estate Residential Secured For Business Purpose [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	1,368	3,726
Real Estate Residential Secured For Business Purpose [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	1,293	603
Real Estate Residential Secured For Business Purpose [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	31	0
Real Estate Residential Secured For Business Purpose [Member] | Financial Asset Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	2,692	4,329
Real Estate Residential Secured For Business Purpose [Member] | Financial Asset Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	401,927	374,331
Real Estate-Residential Secured For Personal Purpose [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	513,330	487,600
Accruing loans and leases	511,170	485,514
Total nonaccrual loans and lease	2,160	2,086
Loans and leases held for investment	513,330	487,600	462,512
Real Estate-Residential Secured For Personal Purpose [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	1,695	6,057
Real Estate-Residential Secured For Personal Purpose [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	761	80
Real Estate-Residential Secured For Personal Purpose [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	0	0
Real Estate-Residential Secured For Personal Purpose [Member] | Financial Asset Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	2,456	6,137
Real Estate-Residential Secured For Personal Purpose [Member] | Financial Asset Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	508,714	479,377
Real Estate Home Equity Secured For Personal Purpose [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	160,018	166,609
Accruing loans and leases	159,235	165,562
Total nonaccrual loans and lease	783	1,047
Loans and leases held for investment	160,018	166,609	173,041
Real Estate Home Equity Secured For Personal Purpose [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	562	607
Real Estate Home Equity Secured For Personal Purpose [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	0	32
Real Estate Home Equity Secured For Personal Purpose [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	0	0
Real Estate Home Equity Secured For Personal Purpose [Member] | Financial Asset Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	562	639
Real Estate Home Equity Secured For Personal Purpose [Member] | Financial Asset Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	158,673	164,923
Loans to Individuals [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	25,845	27,482
Accruing loans and leases	25,845	27,482
Total nonaccrual loans and lease	0	0
Loans and leases held for investment	25,845	27,482	29,222
Loans to Individuals [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	69	190
Loans to Individuals [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	38	74
Loans to Individuals [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	19	185
Loans to Individuals [Member] | Financial Asset Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	126	449
Loans to Individuals [Member] | Financial Asset Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	25,719	27,033
Lease Financings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	171,538	165,039
Accruing loans and leases	171,532	164,832
Total nonaccrual loans and lease	6	207
Loans and leases held for investment	171,538	165,039	$ 154,249
Lease Financings [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	242	898
Lease Financings [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	94	291
Lease Financings [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	87	212
Lease Financings [Member] | Financial Asset Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	423	1,401
Lease Financings [Member] | Financial Asset Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivables, gross	$ 171,109	$ 163,431