Loans and Leases - Credit Quality Indicators (Details) - USD ($)	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases held for investment	$ 5,327,313,000	$ 5,306,841,000	$ 4,951,809,000
2021	876,707,000	2,001,595,000
2020	1,415,068,000	723,898,000
2019	659,739,000	395,275,000
2018	307,382,000	362,654,000
2017	316,264,000	205,604,000
Prior	354,292,000	254,149,000
Revolving loans amortized cost basis	527,130,000	516,936,000
Total	4,456,582,000	4,460,111,000
Nonperforming Financial Instruments [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	106,000	678,000
2020	651,000	182,000
2019	20,000	259,000
2018	558,000	205,000
2017	10,000	7,000
Prior	1,138,000	1,431,000
Revolving loans amortized cost basis	624,000	1,028,000
Total	3,107,000	3,790,000
Performing Financial Instruments [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	170,613,000	267,150,000
2020	240,610,000	110,092,000
2019	83,048,000	88,792,000
2018	54,460,000	64,197,000
2017	40,056,000	43,329,000
Prior	105,126,000	89,160,000
Revolving loans amortized cost basis	173,711,000	180,220,000
Total	867,624,000	842,940,000
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2021	874,073,000	1,966,242,000
2020	1,353,635,000	707,620,000
2019	628,808,000	390,152,000
2018	301,563,000	350,602,000
2017	313,094,000	201,130,000
Prior	340,465,000	238,726,000
Revolving loans amortized cost basis	512,643,000	499,565,000
Total	4,324,281,000	4,354,037,000
Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2021	2,509,000	31,522,000
2020	28,288,000	10,859,000
2019	26,745,000	4,002,000
2018	3,917,000	577,000
2017	1,250,000	2,202,000
Prior	9,006,000	7,144,000
Revolving loans amortized cost basis	7,545,000	9,565,000
Total	79,260,000	65,871,000
Grade 3: Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	125,000	3,831,000
2020	33,145,000	5,419,000
2019	4,186,000	1,121,000
2018	1,902,000	11,475,000
2017	1,920,000	2,272,000
Prior	4,821,000	8,279,000
Revolving loans amortized cost basis	6,942,000	7,806,000
Total	53,041,000	40,203,000
Grade 4: Doubtful [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases held for investment	0
Commercial Financial And Agricultural [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases held for investment	920,621,000	892,665,000	822,733,000
2021	113,565,000	165,270,000
2020	119,795,000	95,180,000
2019	78,417,000	75,400,000
2018	65,844,000	39,434,000
2017	31,737,000	18,148,000
Prior	60,602,000	57,824,000
Revolving loans amortized cost basis	450,661,000	441,409,000
Total	920,621,000	892,665,000
Commercial Financial And Agricultural [Member] | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2021	113,440,000	162,547,000
2020	117,162,000	93,967,000
2019	77,601,000	74,722,000
2018	65,416,000	38,906,000
2017	31,339,000	17,371,000
Prior	58,679,000	56,053,000
Revolving loans amortized cost basis	438,655,000	427,336,000
Total	902,292,000	870,902,000
Commercial Financial And Agricultural [Member] | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	2,723,000
2020	2,633,000	783,000
2019	782,000	316,000
2018	285,000	500,000
2017	383,000	777,000
Prior	1,610,000	1,144,000
Revolving loans amortized cost basis	6,264,000	8,318,000
Total	11,957,000	14,561,000
Commercial Financial And Agricultural [Member] | Grade 3: Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	125,000	0
2020	0	430,000
2019	34,000	362,000
2018	143,000	28,000
2017	15,000	0
Prior	313,000	627,000
Revolving loans amortized cost basis	5,742,000	5,755,000
Total	6,372,000	7,202,000
Real-Estate Commercial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases held for investment	2,600,919,000	2,458,872,000	2,222,490,000
2021	411,443,000	1,094,180,000
2020	995,788,000	496,071,000
2019	475,377,000	227,853,000
2018	185,607,000	279,619,000
2017	247,648,000	145,498,000
Prior	244,663,000	170,063,000
Revolving loans amortized cost basis	40,393,000	45,588,000
Total	2,600,919,000	2,458,872,000
Real-Estate Commercial [Member] | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2021	408,934,000	1,084,157,000
2020	957,849,000	481,997,000
2019	446,367,000	223,646,000
2018	180,449,000	268,236,000
2017	245,775,000	143,041,000
Prior	236,338,000	157,503,000
Revolving loans amortized cost basis	38,710,000	43,008,000
Total	2,514,422,000	2,401,588,000
Real-Estate Commercial [Member] | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2021	2,509,000	6,220,000
2020	4,794,000	10,076,000
2019	25,742,000	3,498,000
2018	3,447,000	0
2017	0	1,250,000
Prior	5,751,000	5,870,000
Revolving loans amortized cost basis	1,281,000	1,247,000
Total	43,524,000	28,161,000
Real-Estate Commercial [Member] | Grade 3: Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	3,803,000
2020	33,145,000	3,998,000
2019	3,268,000	709,000
2018	1,711,000	11,383,000
2017	1,873,000	1,207,000
Prior	2,574,000	6,690,000
Revolving loans amortized cost basis	402,000	1,333,000
Total	42,973,000	29,123,000
Real-Estate Construction [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases held for investment	274,529,000	243,355,000	212,534,000
2021	85,521,000	138,065,000
2020	114,873,000	59,507,000
2019	46,937,000	39,009,000
2018	15,797,000	113,000
2017	991,000	2,950,000
Prior	3,020,000	0
Revolving loans amortized cost basis	7,390,000	3,711,000
Total	274,529,000	243,355,000
Real-Estate Construction [Member] | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2021	85,521,000	116,840,000
2020	94,373,000	59,507,000
2019	46,937,000	39,009,000
2018	15,797,000	113,000
2017	199,000	2,950,000
Prior	3,020,000	0
Revolving loans amortized cost basis	7,390,000	3,711,000
Total	253,237,000	222,130,000
Real-Estate Construction [Member] | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	21,225,000
2020	20,500,000	0
2019	0	0
2018	0	0
2017	792,000	0
Prior	0	0
Revolving loans amortized cost basis	0	0
Total	21,292,000	21,225,000
Real-Estate Construction [Member] | Grade 3: Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	0
2019	0	0
2018	0	0
2017	0	0
Prior	0	0
Revolving loans amortized cost basis	0	0
Total	0	0
Real Estate Residential Secured For Business Purpose [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases held for investment	407,664,000	381,446,000	376,050,000
2021	100,638,000	120,307,000
2020	97,303,000	73,140,000
2019	59,008,000	53,013,000
2018	40,134,000	43,488,000
2017	35,888,000	39,008,000
Prior	46,007,000	26,262,000
Revolving loans amortized cost basis	28,686,000	26,228,000
Total	407,664,000	381,446,000
Real Estate Residential Secured For Business Purpose [Member] | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2021	100,638,000	118,925,000
2020	96,942,000	72,149,000
2019	57,903,000	52,775,000
2018	39,901,000	43,347,000
2017	35,781,000	37,768,000
Prior	42,428,000	25,170,000
Revolving loans amortized cost basis	27,888,000	25,510,000
Total	401,481,000	375,644,000
Real Estate Residential Secured For Business Purpose [Member] | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	1,354,000
2020	361,000	0
2019	221,000	188,000
2018	185,000	77,000
2017	75,000	175,000
Prior	1,645,000	130,000
Revolving loans amortized cost basis	0	0
Total	2,487,000	1,924,000
Real Estate Residential Secured For Business Purpose [Member] | Grade 3: Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	28,000
2020	0	991,000
2019	884,000	50,000
2018	48,000	64,000
2017	32,000	1,065,000
Prior	1,934,000	962,000
Revolving loans amortized cost basis	798,000	718,000
Total	3,696,000	3,878,000
Real Estate-Residential Secured For Personal Purpose [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases held for investment	513,330,000	487,600,000	462,512,000
2021	130,477,000	192,653,000
2020	176,418,000	61,880,000
2019	43,250,000	56,370,000
2018	30,866,000	50,983,000
2017	31,029,000	38,975,000
Prior	100,473,000	85,502,000
Revolving loans amortized cost basis	817,000	1,237,000
Total	513,330,000	487,600,000
Real Estate-Residential Secured For Personal Purpose [Member] | Nonperforming Financial Instruments [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	106,000	666,000
2020	651,000	0
2019	0	56,000
2018	373,000	0
2017	0	0
Prior	1,030,000	1,364,000
Revolving loans amortized cost basis	0	0
Total	2,160,000	2,086,000
Real Estate-Residential Secured For Personal Purpose [Member] | Performing Financial Instruments [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	130,371,000	191,987,000
2020	175,767,000	61,880,000
2019	43,250,000	56,314,000
2018	30,493,000	50,983,000
2017	31,029,000	38,975,000
Prior	99,443,000	84,138,000
Revolving loans amortized cost basis	817,000	1,237,000
Total	511,170,000	485,514,000
Real Estate Home Equity Secured For Personal Purpose [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases held for investment	160,018,000	166,609,000	173,041,000
2021	665,000	1,195,000
2020	1,017,000	815,000
2019	528,000	1,027,000
2018	728,000	1,160,000
2017	963,000	518,000
Prior	2,133,000	2,225,000
Revolving loans amortized cost basis	153,984,000	159,669,000
Total	160,018,000	166,609,000
Real Estate Home Equity Secured For Personal Purpose [Member] | Nonperforming Financial Instruments [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	0
2019	0	198,000
2018	183,000	0
2017	0	0
Prior	28,000	36,000
Revolving loans amortized cost basis	624,000	866,000
Total	835,000	1,100,000
Real Estate Home Equity Secured For Personal Purpose [Member] | Performing Financial Instruments [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	665,000	1,195,000
2020	1,017,000	815,000
2019	528,000	829,000
2018	545,000	1,160,000
2017	963,000	518,000
Prior	2,105,000	2,189,000
Revolving loans amortized cost basis	153,360,000	158,803,000
Total	159,183,000	165,509,000
Loans to Individuals [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases held for investment	25,845,000	27,482,000	29,222,000
2021	1,089,000	1,795,000
2020	1,150,000	1,425,000
2019	1,013,000	970,000
2018	670,000	441,000
2017	247,000	220,000
Prior	2,142,000	2,289,000
Revolving loans amortized cost basis	19,534,000	20,342,000
Total	25,845,000	27,482,000
Loans to Individuals [Member] | Nonperforming Financial Instruments [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	0
2019	0	0
2018	0	0
2017	0	0
Prior	19,000	23,000
Revolving loans amortized cost basis	0	162,000
Total	19,000	185,000
Loans to Individuals [Member] | Performing Financial Instruments [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	1,089,000	1,795,000
2020	1,150,000	1,425,000
2019	1,013,000	970,000
2018	670,000	441,000
2017	247,000	220,000
Prior	2,123,000	2,266,000
Revolving loans amortized cost basis	19,534,000	20,180,000
Total	25,826,000	27,297,000
Lease Financings [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases held for investment	171,538,000	165,039,000	$ 154,249,000
2021	38,488,000	72,185,000
2020	62,676,000	46,154,000
2019	38,277,000	30,684,000
2018	22,754,000	11,818,000
2017	7,827,000	3,623,000
Prior	1,516,000	575,000
Revolving loans amortized cost basis	0	0
Total	171,538,000	165,039,000
Lease Financings [Member] | Nonperforming Financial Instruments [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	12,000
2020	0	182,000
2019	20,000	5,000
2018	2,000	205,000
2017	10,000	7,000
Prior	61,000	8,000
Revolving loans amortized cost basis	0	0
Total	93,000	419,000
Lease Financings [Member] | Performing Financial Instruments [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	38,488,000	72,173,000
2020	62,676,000	45,972,000
2019	38,257,000	30,679,000
2018	22,752,000	11,613,000
2017	7,817,000	3,616,000
Prior	1,455,000	567,000
Revolving loans amortized cost basis	0	0
Total	171,445,000	164,620,000
Financing Receivable [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	170,719,000	267,828,000
2020	241,261,000	110,274,000
2019	83,068,000	89,051,000
2018	55,018,000	64,402,000
2017	40,066,000	43,336,000
Prior	106,264,000	90,591,000
Revolving loans amortized cost basis	174,335,000	181,248,000
Total	$ 870,731,000	$ 846,730,000