Loans - Past Due Financing Receivables (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	$ 4,775,965	$ 3,788,998
Nonaccrual	26,476	19,524
Total financing receivables	4,825,214	3,817,377
Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	19,607	8,082
Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	2,640	773
Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	526	0
Real Estate | Construction and land development
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total financing receivables	443,568	343,125
Real Estate | Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total financing receivables	2,132,066	1,639,992
Real Estate | Residential real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total financing receivables	1,324,377	1,038,810
Commercial and financial | Commercial and financial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total financing receivables	722,322	606,014
Consumer | Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total financing receivables	202,881	189,436
Portfolio Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	3,557,127	2,903,109
Nonaccrual	15,783	12,569
Total financing receivables	3,588,251	2,922,609
Portfolio Loans | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	12,296	6,245
Portfolio Loans | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	2,609	686
Portfolio Loans | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	436	0
Portfolio Loans | Real Estate | Construction and land development
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	301,348	215,077
Nonaccrual	28	238
Total financing receivables	301,473	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 receivables past due	97	0
Portfolio Loans | Real Estate | Construction and land development | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables 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 receivables past due	0	0
Portfolio Loans | Real Estate | Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	1,427,413	1,165,738
Nonaccrual	6,486	1,690
Total financing receivables	1,437,989	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 receivables past due	3,852	2,605
Portfolio Loans | Real Estate | Commercial real estate | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	97	585
Portfolio Loans | Real Estate | Commercial real estate | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	141	0
Portfolio Loans | Real Estate | Residential real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	1,044,375	836,117
Nonaccrual	7,806	8,416
Total financing receivables	1,055,525	845,420
Portfolio Loans | Real Estate | Residential real estate | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	2,524	812
Portfolio Loans | Real Estate | Residential real estate | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	525	75
Portfolio Loans | Real Estate | Residential real estate | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	295	0
Portfolio Loans | Commercial and financial | Commercial and financial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	594,930	507,501
Nonaccrual	1,280	2,127
Total financing receivables	603,057	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 receivables past due	5,186	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 receivables past due	1,661	26
Portfolio Loans | Commercial and financial | Commercial and financial | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	0	0
Portfolio Loans | Consumer | Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	189,061	178,676
Nonaccrual	183	98
Total financing receivables	190,207	178,826
Portfolio Loans | Consumer | Consumer | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	637	52
Portfolio Loans | Consumer | Consumer | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	326	0
Portfolio Loans | Consumer | Consumer | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	0	0
PULs
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	1,209,670	874,028
Nonaccrual	7,096	2,041
Total financing receivables	1,222,529	877,351
PULs | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	5,642	1,195
PULs | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	31	87
PULs | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	90	0
PULs | Real Estate | Construction and land development
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	140,013	126,655
Nonaccrual	0	0
Total financing receivables	141,944	126,689
PULs | Real Estate | Construction and land development | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	1,931	34
PULs | Real Estate | Construction and land development | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables 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 receivables past due	0	0
PULs | Real Estate | Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	680,060	457,899
Nonaccrual	1,343	720
Total financing receivables	683,249	459,598
PULs | Real Estate | Commercial real estate | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	1,846	979
PULs | Real Estate | Commercial real estate | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	0	0
PULs | Real Estate | Commercial real estate | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	0	0
PULs | Real Estate | Residential real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	260,781	186,549
Nonaccrual	3,740	1,000
Total financing receivables	266,134	187,764
PULs | Real Estate | Residential real estate | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	1,523	128
PULs | Real Estate | Residential real estate | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	0	87
PULs | Real Estate | Residential real estate | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	90	0
PULs | Commercial and financial | Commercial and financial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	116,173	92,315
Nonaccrual	2,013	321
Total financing receivables	118,528	92,690
PULs | Commercial and financial | Commercial and financial | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	342	54
PULs | Commercial and financial | Commercial and financial | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	0	0
PULs | Commercial and financial | Commercial and financial | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	0	0
PULs | Consumer | Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	12,643	10,610
Nonaccrual	0	0
Total financing receivables	12,674	10,610
PULs | Consumer | Consumer | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	0	0
PULs | Consumer | Consumer | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	31	0
PULs | Consumer | Consumer | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	0	0
PCI Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	9,168	11,861
Nonaccrual	3,597	4,914
Total financing receivables	14,434	17,417
PCI Loans | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	1,669	642
PCI Loans | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	0	0
PCI Loans | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	0	0
PCI Loans | Real Estate | Construction and land development
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	135	1,121
Nonaccrual	16	0
Total financing receivables	151	1,121
PCI Loans | Real Estate | Construction and land development | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	0	0
PCI Loans | Real Estate | Construction and land development | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	0	0
PCI Loans | Real Estate | Construction and land development | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	0	0
PCI Loans | Real Estate | Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	8,403	9,352
Nonaccrual	1,391	424
Total financing receivables	10,828	9,776
PCI Loans | Real Estate | Commercial real estate | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	1,034	0
PCI Loans | Real Estate | Commercial real estate | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	0	0
PCI Loans | Real Estate | Commercial real estate | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	0	0
PCI Loans | Real Estate | Residential real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	556	544
Nonaccrual	2,162	4,440
Total financing receivables	2,718	5,626
PCI Loans | Real Estate | Residential real estate | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	0	642
PCI Loans | Real Estate | Residential real estate | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	0	0
PCI Loans | Real Estate | Residential real estate | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	0	0
PCI Loans | Commercial and financial | Commercial and financial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	74	844
Nonaccrual	28	50
Total financing receivables	737	894
PCI Loans | Commercial and financial | Commercial and financial | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	635	0
PCI Loans | Commercial and financial | Commercial and financial | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	0	0
PCI Loans | Commercial and financial | Commercial and financial | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	0	0
PCI Loans | Consumer | Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	0	0
Nonaccrual	0	0
Total financing receivables	0	0
PCI Loans | Consumer | Consumer | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	0	0
PCI Loans | Consumer | Consumer | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	0	0
PCI Loans | Consumer | Consumer | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables past due	$ 0	$ 0