Loans - Past Due Financing Receivables (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	$ 4,014,200	$ 3,788,998
Nonaccrual	26,140	19,524
Total Financing Receivables	4,059,323	3,817,377
Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	14,446	8,082
Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	3,482	773
Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	1,055	0
Real Estate | Construction and land development
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	376,257	343,125
Real Estate | Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	1,726,699	1,639,992
Real Estate | Residential real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	1,152,640	1,038,810
Commercial and financial | Commercial and financial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	610,955	606,014
Consumer | Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	192,772	189,436
Portfolio Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	3,354,045	2,903,109
Nonaccrual	18,998	12,569
Total Financing Receivables	3,383,571	2,922,609
Portfolio Loans | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	7,544	6,245
Portfolio Loans | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	2,625	686
Portfolio Loans | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	359	0
Portfolio Loans | Real Estate | Construction and land development
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	289,234	215,077
Nonaccrual	215	238
Total Financing Receivables	289,449	215,315
Portfolio Loans | Real Estate | Construction and land development | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Portfolio Loans | Real Estate | Construction and land development | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Portfolio Loans | Real Estate | Construction and land development | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Portfolio Loans | Real Estate | Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	1,345,174	1,165,738
Nonaccrual	9,374	1,690
Total Financing Receivables	1,357,721	1,170,618
Portfolio Loans | Real Estate | Commercial real estate | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	3,173	2,605
Portfolio Loans | Real Estate | Commercial real estate | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	585
Portfolio Loans | Real Estate | Commercial real estate | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Portfolio Loans | Real Estate | Residential real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	984,874	836,117
Nonaccrual	8,395	8,416
Total Financing Receivables	994,575	845,420
Portfolio Loans | Real Estate | Residential real estate | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	1,202	812
Portfolio Loans | Real Estate | Residential real estate | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	104	75
Portfolio Loans | Real Estate | Residential real estate | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Portfolio Loans | Commercial and financial | Commercial and financial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	548,861	507,501
Nonaccrual	836	2,127
Total Financing Receivables	554,627	512,430
Portfolio Loans | Commercial and financial | Commercial and financial | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	2,050	2,776
Portfolio Loans | Commercial and financial | Commercial and financial | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	2,521	26
Portfolio Loans | Commercial and financial | Commercial and financial | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	359	0
Portfolio Loans | Consumer | Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	185,902	178,676
Nonaccrual	178	98
Total Financing Receivables	187,199	178,826
Portfolio Loans | Consumer | Consumer | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	1,119	52
Portfolio Loans | Consumer | Consumer | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Portfolio Loans | Consumer | Consumer | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
PULs
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	649,340	874,028
Nonaccrual	4,906	2,041
Total Financing Receivables	662,701	877,351
PULs | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	6,902	1,195
PULs | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	857	87
PULs | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	696	0
PULs | Real Estate | Construction and land development
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	86,679	126,655
Nonaccrual	0	0
Total Financing Receivables	86,679	126,689
PULs | Real Estate | Construction and land development | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	34
PULs | Real Estate | Construction and land development | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
PULs | Real Estate | Construction and land development | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
PULs | Real Estate | Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	355,541	457,899
Nonaccrual	722	720
Total Financing Receivables	358,140	459,598
PULs | Real Estate | Commercial real estate | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	1,181	979
PULs | Real Estate | Commercial real estate | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
PULs | Real Estate | Commercial real estate | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	696	0
PULs | Real Estate | Residential real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	151,125	186,549
Nonaccrual	3,755	1,000
Total Financing Receivables	156,709	187,764
PULs | Real Estate | Residential real estate | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	1,705	128
PULs | Real Estate | Residential real estate | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	124	87
PULs | Real Estate | Residential real estate | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
PULs | Commercial and financial | Commercial and financial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	50,427	92,315
Nonaccrual	429	321
Total Financing Receivables	55,600	92,690
PULs | Commercial and financial | Commercial and financial | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	4,011	54
PULs | Commercial and financial | Commercial and financial | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	733	0
PULs | Commercial and financial | Commercial and financial | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
PULs | Consumer | Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	5,568	10,610
Nonaccrual	0	0
Total Financing Receivables	5,573	10,610
PULs | Consumer | Consumer | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	5	0
PULs | Consumer | Consumer | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
PULs | Consumer | Consumer | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Credit Impaired Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	10,815	11,861
Nonaccrual	2,236	4,914
Total Financing Receivables	13,051	17,417
Purchased Credit Impaired Loans | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	642
Purchased Credit Impaired Loans | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Credit Impaired Loans | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Credit Impaired Loans | Real Estate | Construction and land development
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	129	1,121
Nonaccrual	0	0
Total Financing Receivables	129	1,121
Purchased Credit Impaired Loans | Real Estate | Construction and land development | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Credit Impaired Loans | Real Estate | Construction and land development | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Credit Impaired Loans | Real Estate | Construction and land development | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Credit Impaired Loans | Real Estate | Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	9,427	9,352
Nonaccrual	1,411	424
Total Financing Receivables	10,838	9,776
Purchased Credit Impaired Loans | Real Estate | Commercial real estate | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Credit Impaired Loans | Real Estate | Commercial real estate | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Credit Impaired Loans | Real Estate | Commercial real estate | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Credit Impaired Loans | Real Estate | Residential real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	552	544
Nonaccrual	804	4,440
Total Financing Receivables	1,356	5,626
Purchased Credit Impaired Loans | Real Estate | Residential real estate | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	642
Purchased Credit Impaired Loans | Real Estate | Residential real estate | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Credit Impaired Loans | Real Estate | Residential real estate | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Credit Impaired Loans | Commercial and financial | Commercial and financial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	707	844
Nonaccrual	21	50
Total Financing Receivables	728	894
Purchased Credit Impaired Loans | Commercial and financial | Commercial and financial | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Credit Impaired Loans | Commercial and financial | Commercial and financial | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Credit Impaired Loans | Commercial and financial | Commercial and financial | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Credit Impaired Loans | Consumer | Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	0	0
Nonaccrual	0	0
Total Financing Receivables	0	0
Purchased Credit Impaired Loans | Consumer | Consumer | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Credit Impaired Loans | Consumer | Consumer | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Credit Impaired Loans | Consumer | Consumer | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	$ 0	$ 0