Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI - Aging Analysis of Past Due and Nonaccrual LHFI by Loan Type (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	$ 29,906	$ 24,471
Nonaccrual	51,448	63,128
Current Loans	10,122,963	9,800,053
Total LHFI	10,152,869	9,824,524
Past Due 30 to 59 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	5,685	9,615
Past Due 60 to 89 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	7,430	5,304
Past Due 90 Days or More [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	16,791	9,552
Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	6,131	534
Nonaccrual	6,165	5,985
Current Loans	526,506	513,522
Total LHFI	532,637	514,056
Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member] | Past Due 30 to 59 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	352	339
Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member] | Past Due 60 to 89 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	5,583	34
Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member] | Past Due 90 Days or More [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	196	161
Other Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	2,501	2,924
Nonaccrual	3,731	4,487
Current Loans	505,232	521,808
Total LHFI	507,733	524,732
Other Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member] | Past Due 30 to 59 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	1,160	1,505
Other Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member] | Past Due 60 to 89 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	538	523
Other Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member] | Past Due 90 Days or More [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	803	896
Secured by 1-4 Family Residential Properties [Member] | Other Loans Secured by Real Estate [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	9,107	9,690
Nonaccrual	12,222	11,807
Current Loans	1,293,556	1,206,710
Total LHFI	1,302,663	1,216,400
Secured by 1-4 Family Residential Properties [Member] | Other Loans Secured by Real Estate [Member] | Past Due 30 to 59 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	2,230	3,291
Secured by 1-4 Family Residential Properties [Member] | Other Loans Secured by Real Estate [Member] | Past Due 60 to 89 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	1,061	1,289
Secured by 1-4 Family Residential Properties [Member] | Other Loans Secured by Real Estate [Member] | Past Due 90 Days or More [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	5,816	5,110
Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	1,138	1,892
Nonaccrual	13,563	15,197
Current Loans	2,818,524	2,707,134
Total LHFI	2,819,662	2,709,026
Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member] | Past Due 30 to 59 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	422	920
Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member] | Past Due 60 to 89 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	23
Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member] | Past Due 90 Days or More [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	693	972
Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	170	311
Nonaccrual	175	185
Current Loans	1,078,452	1,065,653
Total LHFI	1,078,622	1,065,964
Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member] | Past Due 30 to 59 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	63	103
Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member] | Past Due 60 to 89 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		101
Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member] | Past Due 90 Days or More [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	107	107
Commercial and Industrial Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	4,153	2,010
Nonaccrual	6,042	15,618
Current Loans	1,322,452	1,307,068
Total LHFI	1,326,605	1,309,078
Commercial and Industrial Loans [Member] | Past Due 30 to 59 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	291	271
Commercial and Industrial Loans [Member] | Past Due 60 to 89 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	65	196
Commercial and Industrial Loans [Member] | Past Due 90 Days or More [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	3,797	1,543
Other Construction [Member] | Other Loans Secured by Real Estate [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Current Loans	827,665	794,983
Total LHFI	827,665	794,983
Consumer Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	970	1,356
Nonaccrual	53	86
Current Loans	155,105	163,030
Total LHFI	156,075	164,386
Consumer Loans [Member] | Past Due 30 to 59 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	767	926
Consumer Loans [Member] | Past Due 60 to 89 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	87	190
Consumer Loans [Member] | Past Due 90 Days or More [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	116	240
State and Other Political Subdivision Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	177	294
Nonaccrual	3,854	3,970
Current Loans	1,136,587	1,000,482
Total LHFI	1,136,764	1,000,776
State and Other Political Subdivision Loans [Member] | Past Due 30 to 59 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		117
State and Other Political Subdivision Loans [Member] | Past Due 90 Days or More [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	177	177
Other Commercial Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	5,559	5,460
Nonaccrual	5,643	5,793
Current Loans	458,884	519,663
Total LHFI	464,443	525,123
Other Commercial Loans [Member] | Past Due 30 to 59 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	400	2,143
Other Commercial Loans [Member] | Past Due 60 to 89 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	73	2,971
Other Commercial Loans [Member] | Past Due 90 Days or More [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	$ 5,086	$ 346