Loans and Leases - Credit Quality Indicators (Details) - USD ($)	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases held for investment	$ 5,252,045,000	$ 5,306,841,000	$ 5,211,856,000
2021	1,045,657,000	2,001,595,000
2020	1,239,863,000	723,898,000
2019	638,818,000	395,275,000
2018	301,443,000	362,654,000
2017	290,876,000	205,604,000
Prior	301,164,000	254,149,000
Revolving loans amortized cost basis	537,568,000	516,936,000
Total	4,355,389,000	4,460,111,000
Nonperforming Financial Instruments [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	77,000	678,000
2020	659,000	182,000
2019	66,000	259,000
2018	565,000	205,000
2017	5,000	7,000
Prior	1,188,000	1,431,000
Revolving loans amortized cost basis	525,000	1,028,000
Total	3,085,000	3,790,000
Performing Financial Instruments [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	235,948,000	267,150,000
2020	230,838,000	110,092,000
2019	72,569,000	88,792,000
2018	47,960,000	64,197,000
2017	33,415,000	43,329,000
Prior	99,141,000	89,160,000
Revolving loans amortized cost basis	173,700,000	180,220,000
Total	893,571,000	842,940,000
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2021	1,040,134,000	1,966,242,000
2020	1,190,994,000	707,620,000
2019	607,035,000	390,152,000
2018	275,429,000	350,602,000
2017	287,503,000	201,130,000
Prior	284,802,000	238,726,000
Revolving loans amortized cost basis	515,774,000	499,565,000
Total	4,201,671,000	4,354,037,000
Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2021	5,523,000	31,522,000
2020	16,798,000	10,859,000
2019	28,348,000	4,002,000
2018	23,861,000	577,000
2017	1,480,000	2,202,000
Prior	8,163,000	7,144,000
Revolving loans amortized cost basis	15,932,000	9,565,000
Total	100,105,000	65,871,000
Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	3,831,000
2020	32,071,000	5,419,000
2019	3,435,000	1,121,000
2018	2,153,000	11,475,000
2017	1,893,000	2,272,000
Prior	8,199,000	8,279,000
Revolving loans amortized cost basis	5,862,000	7,806,000
Total	53,613,000	40,203,000
Doubtful
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	927,015,000	892,665,000	894,314,000
2021	148,549,000	165,270,000
2020	106,679,000	95,180,000
2019	77,831,000	75,400,000
2018	56,203,000	39,434,000
2017	26,361,000	18,148,000
Prior	55,379,000	57,824,000
Revolving loans amortized cost basis	456,013,000	441,409,000
Total	927,015,000	892,665,000
Commercial Financial And Agricultural [Member] | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2021	148,549,000	162,547,000
2020	101,422,000	93,967,000
2019	75,241,000	74,722,000
2018	55,694,000	38,906,000
2017	25,859,000	17,371,000
Prior	53,712,000	56,053,000
Revolving loans amortized cost basis	436,226,000	427,336,000
Total	896,703,000	870,902,000
Commercial Financial And Agricultural [Member] | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	2,723,000
2020	5,257,000	783,000
2019	2,560,000	316,000
2018	440,000	500,000
2017	487,000	777,000
Prior	1,372,000	1,144,000
Revolving loans amortized cost basis	14,609,000	8,318,000
Total	24,725,000	14,561,000
Commercial Financial And Agricultural [Member] | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	430,000
2019	30,000	362,000
2018	69,000	28,000
2017	15,000	0
Prior	295,000	627,000
Revolving loans amortized cost basis	5,178,000	5,755,000
Total	5,587,000	7,202,000
Real-Estate Commercial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases held for investment	2,669,898,000	2,458,872,000	2,369,691,000
2021	584,932,000	1,094,180,000
2020	969,401,000	496,071,000
2019	457,283,000	227,853,000
2018	172,684,000	279,619,000
2017	232,320,000	145,498,000
Prior	208,535,000	170,063,000
Revolving loans amortized cost basis	44,743,000	45,588,000
Total	2,669,898,000	2,458,872,000
Real-Estate Commercial [Member] | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2021	582,442,000	1,084,157,000
2020	927,367,000	481,997,000
2019	428,304,000	223,646,000
2018	167,225,000	268,236,000
2017	229,552,000	143,041,000
Prior	197,290,000	157,503,000
Revolving loans amortized cost basis	43,313,000	43,008,000
Total	2,575,493,000	2,401,588,000
Real-Estate Commercial [Member] | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2021	2,490,000	6,220,000
2020	9,963,000	10,076,000
2019	25,574,000	3,498,000
2018	3,421,000	0
2017	919,000	1,250,000
Prior	5,691,000	5,870,000
Revolving loans amortized cost basis	1,323,000	1,247,000
Total	49,381,000	28,161,000
Real-Estate Commercial [Member] | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	3,803,000
2020	32,071,000	3,998,000
2019	3,405,000	709,000
2018	2,038,000	11,383,000
2017	1,849,000	1,207,000
Prior	5,554,000	6,690,000
Revolving loans amortized cost basis	107,000	1,333,000
Total	45,024,000	29,123,000
Real-Estate Construction [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases held for investment	260,874,000	243,355,000	233,590,000
2021	100,190,000	138,065,000
2020	66,937,000	59,507,000
2019	47,603,000	39,009,000
2018	36,330,000	113,000
2017	198,000	2,950,000
Prior	0	0
Revolving loans amortized cost basis	9,616,000	3,711,000
Total	260,874,000	243,355,000
Real-Estate Construction [Member] | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2021	97,157,000	116,840,000
2020	66,437,000	59,507,000
2019	47,603,000	39,009,000
2018	16,330,000	113,000
2017	198,000	2,950,000
Prior	0	0
Revolving loans amortized cost basis	9,616,000	3,711,000
Total	237,341,000	222,130,000
Real-Estate Construction [Member] | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2021	3,033,000	21,225,000
2020	500,000	0
2019	0	0
2018	20,000,000	0
2017	0	0
Prior	0	0
Revolving loans amortized cost basis	0	0
Total	23,533,000	21,225,000
Real-Estate Construction [Member] | Substandard
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	412,001,000	381,446,000	378,239,000
2021	131,220,000	120,307,000
2020	92,011,000	73,140,000
2019	56,101,000	53,013,000
2018	36,226,000	43,488,000
2017	31,997,000	39,008,000
Prior	37,250,000	26,262,000
Revolving loans amortized cost basis	27,196,000	26,228,000
Total	412,001,000	381,446,000
Real Estate Residential Secured For Business Purpose [Member] | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2021	131,220,000	118,925,000
2020	90,933,000	72,149,000
2019	55,887,000	52,775,000
2018	36,180,000	43,347,000
2017	31,894,000	37,768,000
Prior	33,800,000	25,170,000
Revolving loans amortized cost basis	26,619,000	25,510,000
Total	406,533,000	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	1,078,000	0
2019	214,000	188,000
2018	0	77,000
2017	74,000	175,000
Prior	1,100,000	130,000
Revolving loans amortized cost basis	0	0
Total	2,466,000	1,924,000
Real Estate Residential Secured For Business Purpose [Member] | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	28,000
2020	0	991,000
2019	0	50,000
2018	46,000	64,000
2017	29,000	1,065,000
Prior	2,350,000	962,000
Revolving loans amortized cost basis	577,000	718,000
Total	3,002,000	3,878,000
Real Estate-Residential Secured For Personal Purpose [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases held for investment	535,705,000	487,600,000	474,688,000
2021	174,298,000	192,653,000
2020	172,284,000	61,880,000
2019	38,776,000	56,370,000
2018	27,946,000	50,983,000
2017	26,533,000	38,975,000
Prior	95,653,000	85,502,000
Revolving loans amortized cost basis	215,000	1,237,000
Total	535,705,000	487,600,000
Real Estate-Residential Secured For Personal Purpose [Member] | Nonperforming Financial Instruments [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	54,000	666,000
2020	643,000	0
2019	0	56,000
2018	371,000	0
2017	0	0
Prior	1,011,000	1,364,000
Revolving loans amortized cost basis	0	0
Total	2,079,000	2,086,000
Real Estate-Residential Secured For Personal Purpose [Member] | Performing Financial Instruments [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	174,244,000	191,987,000
2020	171,641,000	61,880,000
2019	38,776,000	56,314,000
2018	27,575,000	50,983,000
2017	26,533,000	38,975,000
Prior	94,642,000	84,138,000
Revolving loans amortized cost basis	215,000	1,237,000
Total	533,626,000	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	159,029,000	166,609,000	172,448,000
2021	641,000	1,195,000
2020	953,000	815,000
2019	478,000	1,027,000
2018	696,000	1,160,000
2017	887,000	518,000
Prior	1,876,000	2,225,000
Revolving loans amortized cost basis	153,498,000	159,669,000
Total	159,029,000	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	182,000	0
2017	0	0
Prior	65,000	36,000
Revolving loans amortized cost basis	525,000	866,000
Total	772,000	1,100,000
Real Estate Home Equity Secured For Personal Purpose [Member] | Performing Financial Instruments [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	641,000	1,195,000
2020	953,000	815,000
2019	478,000	829,000
2018	514,000	1,160,000
2017	887,000	518,000
Prior	1,811,000	2,189,000
Revolving loans amortized cost basis	152,973,000	158,803,000
Total	158,257,000	165,509,000
Loans to Individuals [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases held for investment	26,458,000	27,482,000	27,771,000
2021	1,337,000	1,795,000
2020	1,019,000	1,425,000
2019	850,000	970,000
2018	543,000	441,000
2017	157,000	220,000
Prior	2,040,000	2,289,000
Revolving loans amortized cost basis	20,512,000	20,342,000
Total	26,458,000	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	58,000	23,000
Revolving loans amortized cost basis	0	162,000
Total	58,000	185,000
Loans to Individuals [Member] | Performing Financial Instruments [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	1,337,000	1,795,000
2020	1,019,000	1,425,000
2019	850,000	970,000
2018	543,000	441,000
2017	157,000	220,000
Prior	1,982,000	2,266,000
Revolving loans amortized cost basis	20,512,000	20,180,000
Total	26,400,000	27,297,000
Lease Financings [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases held for investment	175,464,000	165,039,000	$ 159,535,000
2021	59,749,000	72,185,000
2020	16,000	46,154,000
2019	32,531,000	30,684,000
2018	19,340,000	11,818,000
2017	5,843,000	3,623,000
Prior	760,000	575,000
Revolving loans amortized cost basis	0	0
Total	175,464,000	165,039,000
Lease Financings [Member] | Nonperforming Financial Instruments [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	23,000	12,000
2020	16,000	182,000
2019	66,000	5,000
2018	12,000	205,000
2017	5,000	7,000
Prior	54,000	8,000
Revolving loans amortized cost basis	0	0
Total	176,000	419,000
Lease Financings [Member] | Performing Financial Instruments [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	59,726,000	72,173,000
2020	57,225,000	45,972,000
2019	32,465,000	30,679,000
2018	19,328,000	11,613,000
2017	5,838,000	3,616,000
Prior	706,000	567,000
Revolving loans amortized cost basis	0	0
Total	175,288,000	164,620,000
Financing Receivable [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	236,025,000	267,828,000
2020	231,497,000	110,274,000
2019	72,635,000	89,051,000
2018	48,525,000	64,402,000
2017	33,420,000	43,336,000
Prior	100,329,000	90,591,000
Revolving loans amortized cost basis	174,225,000	181,248,000
Total	$ 896,656,000	$ 846,730,000