Loans and Leases - Credit Quality Indicators (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	$ 3,948,957	$ 3,629,198
Total loans and leases held for investment, acquired	302,976	377,376
Grade 1: Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	3,127,479	2,851,733
Total loans and leases held for investment, acquired	238,657	304,928
Grade 2: Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	46,064	55,799
Total loans and leases held for investment, acquired	1,316	0
Grade 3: Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	44,903	31,119
Total loans and leases held for investment, acquired	12,150	13,619
Grade 4: Doubtful [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	0	0
Total loans and leases held for investment, acquired	0	0
Internally assigned grades [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	3,218,446	2,938,651
Total loans and leases held for investment, acquired	252,123	318,547
Performing financing receivable [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	727,772	689,112
Total loans and leases held for investment, acquired	48,951	56,867
Nonperforming financing receivable [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	2,739	1,435
Total loans and leases held for investment, acquired	1,902	1,962
Performing and nonperforming [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	730,511	690,547
Total loans and leases held for investment, acquired	50,853	58,829
Commercial, Financial and Agricultural [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	943,713	913,166
Total loans and leases held for investment, acquired	15,440	24,519
Commercial, Financial and Agricultural [Member] | Grade 1: Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	907,186	882,736
Total loans and leases held for investment, acquired	15,440	24,450
Commercial, Financial and Agricultural [Member] | Grade 2: Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	18,924	23,287
Total loans and leases held for investment, acquired	0	0
Commercial, Financial and Agricultural [Member] | Grade 3: Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	17,603	7,143
Total loans and leases held for investment, acquired	0	69
Commercial, Financial and Agricultural [Member] | Grade 4: Doubtful [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	0	0
Total loans and leases held for investment, acquired	0	0
Commercial, Financial and Agricultural [Member] | Internally assigned grades [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	943,713	913,166
Total loans and leases held for investment, acquired	15,440	24,519
Real Estate-Commercial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	1,736,904	1,507,579
Total loans and leases held for investment, acquired	191,946	233,625
Real Estate-Commercial [Member] | Grade 1: Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	1,690,123	1,455,234
Total loans and leases held for investment, acquired	178,997	220,911
Real Estate-Commercial [Member] | Grade 2: Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	23,667	31,791
Total loans and leases held for investment, acquired	1,316	0
Real Estate-Commercial [Member] | Grade 3: Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	23,114	20,554
Total loans and leases held for investment, acquired	11,633	12,714
Real Estate-Commercial [Member] | Grade 4: Doubtful [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	0	0
Total loans and leases held for investment, acquired	0	0
Real Estate-Commercial [Member] | Internally assigned grades [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	1,736,904	1,507,579
Total loans and leases held for investment, acquired	191,946	233,625
Real Estate-Construction [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	221,845	215,513
Total loans and leases held for investment, acquired	0	0
Real Estate-Construction [Member] | Grade 1: Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	219,656	215,407
Total loans and leases held for investment, acquired	0	0
Real Estate-Construction [Member] | Grade 2: Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	1,932	0
Total loans and leases held for investment, acquired	0	0
Real Estate-Construction [Member] | Grade 3: Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	257	106
Total loans and leases held for investment, acquired	0	0
Real Estate-Construction [Member] | Grade 4: Doubtful [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	0	0
Total loans and leases held for investment, acquired	0	0
Real Estate-Construction [Member] | Internally assigned grades [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	221,845	215,513
Total loans and leases held for investment, acquired	0	0
Real Estate-Residential Secured For Business Purpose [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	315,984	302,393
Total loans and leases held for investment, acquired	44,737	60,403
Real Estate-Residential Secured For Business Purpose [Member] | Grade 1: Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	310,514	298,356
Total loans and leases held for investment, acquired	44,220	59,567
Real Estate-Residential Secured For Business Purpose [Member] | Grade 2: Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	1,541	721
Total loans and leases held for investment, acquired	0	0
Real Estate-Residential Secured For Business Purpose [Member] | Grade 3: Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	3,929	3,316
Total loans and leases held for investment, acquired	517	836
Real Estate-Residential Secured For Business Purpose [Member] | Grade 4: Doubtful [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	0	0
Total loans and leases held for investment, acquired	0	0
Real Estate-Residential Secured For Business Purpose [Member] | Internally assigned grades [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	315,984	302,393
Total loans and leases held for investment, acquired	44,737	60,403
Real Estate-Residential Secured For Personal Purpose [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	388,643	338,451
Total loans and leases held for investment, acquired	43,545	49,959
Real Estate-Residential Secured For Personal Purpose [Member] | Performing financing receivable [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	387,449	337,762
Total loans and leases held for investment, acquired	42,652	49,061
Real Estate-Residential Secured For Personal Purpose [Member] | Nonperforming financing receivable [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	1,194	689
Total loans and leases held for investment, acquired	893	898
Real Estate-Residential Secured For Personal Purpose [Member] | Performing and nonperforming [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	388,643	338,451
Total loans and leases held for investment, acquired	43,545	49,959
Real Estate-Home Equity Secured For Personal Purpose [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	170,486	177,523
Total loans and leases held for investment, acquired	7,168	8,728
Real Estate-Home Equity Secured For Personal Purpose [Member] | Performing financing receivable [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	170,062	177,139
Total loans and leases held for investment, acquired	6,159	7,664
Real Estate-Home Equity Secured For Personal Purpose [Member] | Nonperforming financing receivable [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	424	384
Total loans and leases held for investment, acquired	1,009	1,064
Real Estate-Home Equity Secured For Personal Purpose [Member] | Performing and nonperforming [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	170,486	177,523
Total loans and leases held for investment, acquired	7,168	8,728
Loans to Individuals [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	30,575	32,617
Total loans and leases held for investment, acquired	140	142
Loans to Individuals [Member] | Performing financing receivable [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	30,444	32,562
Total loans and leases held for investment, acquired	140	142
Loans to Individuals [Member] | Nonperforming financing receivable [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	131	55
Total loans and leases held for investment, acquired	0	0
Loans to Individuals [Member] | Performing and nonperforming [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	30,575	32,617
Total loans and leases held for investment, acquired	140	142
Lease Financings [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	140,807	141,956
Total loans and leases held for investment, acquired	0	0
Lease Financings [Member] | Performing financing receivable [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	139,817	141,649
Total loans and leases held for investment, acquired	0	0
Lease Financings [Member] | Nonperforming financing receivable [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	990	307
Total loans and leases held for investment, acquired	0	0
Lease Financings [Member] | Performing and nonperforming [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases held for investment, originated	140,807	141,956
Total loans and leases held for investment, acquired	$ 0	$ 0