Loans - Past Due Financing Receivables (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Financing Receivable, Past Due [Line Items]
Current	$ 4,941,381	$ 4,775,965
Nonaccrual	26,044	26,476
Total Financing Receivables	4,986,289	4,825,214
Accruing 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	13,812	19,607
Accruing 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	5,052	2,640
Accruing Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	526
Construction and land development
Financing Receivable, Past Due [Line Items]
Total Financing Receivables	326,324	443,568
Commercial real estate
Financing Receivable, Past Due [Line Items]
Total Financing Receivables	2,310,367	2,132,066
Residential real estate
Financing Receivable, Past Due [Line Items]
Total Financing Receivables	1,409,946	1,324,377
Commercial and financial
Financing Receivable, Past Due [Line Items]
Total Financing Receivables	722,286	722,322
Consumer
Financing Receivable, Past Due [Line Items]
Total Financing Receivables	217,366	202,881
Portfolio Loans
Financing Receivable, Past Due [Line Items]
Current	3,977,424	3,557,127
Nonaccrual	20,401	15,783
Total Financing Receivables	4,010,299	3,588,251
Portfolio Loans | Accruing 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	11,387	12,296
Portfolio Loans | Accruing 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	1,087	2,609
Portfolio Loans | Accruing Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	436
Portfolio Loans | Construction and land development
Financing Receivable, Past Due [Line Items]
Current	266,815	301,348
Nonaccrual	4,353	28
Total Financing Receivables	272,915	301,473
Portfolio Loans | Construction and land development | Accruing 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	1,747	97
Portfolio Loans | Construction and land development | Accruing 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Portfolio Loans | Construction and land development | Accruing Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Portfolio Loans | Commercial real estate
Financing Receivable, Past Due [Line Items]
Current	1,702,928	1,427,413
Nonaccrual	4,429	6,486
Total Financing Receivables	1,709,227	1,437,989
Portfolio Loans | Commercial real estate | Accruing 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	1,271	3,852
Portfolio Loans | Commercial real estate | Accruing 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	599	97
Portfolio Loans | Commercial real estate | Accruing Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	141
Portfolio Loans | Residential real estate
Financing Receivable, Past Due [Line Items]
Current	1,173,158	1,044,375
Nonaccrual	7,890	7,806
Total Financing Receivables	1,184,579	1,055,525
Portfolio Loans | Residential real estate | Accruing 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	3,349	2,524
Portfolio Loans | Residential real estate | Accruing 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	182	525
Portfolio Loans | Residential real estate | Accruing Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	295
Portfolio Loans | Commercial and financial
Financing Receivable, Past Due [Line Items]
Current	627,056	594,930
Nonaccrual	3,649	1,280
Total Financing Receivables	635,153	603,057
Portfolio Loans | Commercial and financial | Accruing 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	4,448	5,186
Portfolio Loans | Commercial and financial | Accruing 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	1,661
Portfolio Loans | Commercial and financial | Accruing Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Portfolio Loans | Consumer
Financing Receivable, Past Due [Line Items]
Current	207,467	189,061
Nonaccrual	80	183
Total Financing Receivables	208,425	190,207
Portfolio Loans | Consumer | Accruing 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	572	637
Portfolio Loans | Consumer | Accruing 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	306	326
Portfolio Loans | Consumer | Accruing Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Unimpaired Loans
Financing Receivable, Past Due [Line Items]
Current	953,340	1,209,670
Nonaccrual	2,879	7,096
Total Financing Receivables	962,609	1,222,529
Purchased Unimpaired Loans | Accruing 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	2,425	5,642
Purchased Unimpaired Loans | Accruing 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	3,965	31
Purchased Unimpaired Loans | Accruing Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	90
Purchased Unimpaired Loans | Construction and land development
Financing Receivable, Past Due [Line Items]
Current	49,682	140,013
Nonaccrual	574	0
Total Financing Receivables	53,251	141,944
Purchased Unimpaired Loans | Construction and land development | Accruing 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	1,931
Purchased Unimpaired Loans | Construction and land development | Accruing 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	2,995	0
Purchased Unimpaired Loans | Construction and land development | Accruing Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Unimpaired Loans | Commercial real estate
Financing Receivable, Past Due [Line Items]
Current	587,865	680,060
Nonaccrual	1,296	1,343
Total Financing Receivables	590,881	683,249
Purchased Unimpaired Loans | Commercial real estate | Accruing 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	872	1,846
Purchased Unimpaired Loans | Commercial real estate | Accruing 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	848	0
Purchased Unimpaired Loans | Commercial real estate | Accruing Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Unimpaired Loans | Residential real estate
Financing Receivable, Past Due [Line Items]
Current	222,383	260,781
Nonaccrual	423	3,740
Total Financing Receivables	223,003	266,134
Purchased Unimpaired Loans | Residential real estate | Accruing 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	75	1,523
Purchased Unimpaired Loans | Residential real estate | Accruing 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	122	0
Purchased Unimpaired Loans | Residential real estate | Accruing Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	90
Purchased Unimpaired Loans | Commercial and financial
Financing Receivable, Past Due [Line Items]
Current	84,614	116,173
Nonaccrual	557	2,013
Total Financing Receivables	86,533	118,528
Purchased Unimpaired Loans | Commercial and financial | Accruing 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	1,362	342
Purchased Unimpaired Loans | Commercial and financial | Accruing 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Unimpaired Loans | Commercial and financial | Accruing Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Unimpaired Loans | Consumer
Financing Receivable, Past Due [Line Items]
Current	8,796	12,643
Nonaccrual	29	0
Total Financing Receivables	8,941	12,674
Purchased Unimpaired Loans | Consumer | Accruing 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	116	0
Purchased Unimpaired Loans | Consumer | Accruing 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	31
Purchased Unimpaired Loans | Consumer | Accruing Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Credit Impaired Loans
Financing Receivable, Past Due [Line Items]
Current	10,617	9,168
Nonaccrual	2,764	3,597
Total Financing Receivables	13,381	14,434
Purchased Credit Impaired Loans | Accruing 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	1,669
Purchased Credit Impaired Loans | Accruing 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Credit Impaired Loans | Accruing Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Credit Impaired Loans | Construction and land development
Financing Receivable, Past Due [Line Items]
Current	145	135
Nonaccrual	13	16
Total Financing Receivables	158	151
Purchased Credit Impaired Loans | Construction and land development | Accruing 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Credit Impaired Loans | Construction and land development | Accruing 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Credit Impaired Loans | Construction and land development | Accruing Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Credit Impaired Loans | Commercial real estate
Financing Receivable, Past Due [Line Items]
Current	9,314	8,403
Nonaccrual	945	1,391
Total Financing Receivables	10,259	10,828
Purchased Credit Impaired Loans | Commercial real estate | Accruing 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	1,034
Purchased Credit Impaired Loans | Commercial real estate | Accruing 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Credit Impaired Loans | Commercial real estate | Accruing Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Credit Impaired Loans | Residential real estate
Financing Receivable, Past Due [Line Items]
Current	573	556
Nonaccrual	1,791	2,162
Total Financing Receivables	2,364	2,718
Purchased Credit Impaired Loans | Residential real estate | Accruing 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Credit Impaired Loans | Residential real estate | Accruing 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Credit Impaired Loans | Residential real estate | Accruing Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Credit Impaired Loans | Commercial and financial
Financing Receivable, Past Due [Line Items]
Current	585	74
Nonaccrual	15	28
Total Financing Receivables	600	737
Purchased Credit Impaired Loans | Commercial and financial | Accruing 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	635
Purchased Credit Impaired Loans | Commercial and financial | Accruing 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Credit Impaired Loans | Commercial and financial | Accruing Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Credit Impaired Loans | Consumer
Financing Receivable, Past Due [Line Items]
Current	0	0
Nonaccrual	0	0
Total Financing Receivables	0	0
Purchased Credit Impaired Loans | Consumer | Accruing 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Credit Impaired Loans | Consumer | Accruing 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Credit Impaired Loans | Consumer | Accruing Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	$ 0	$ 0