Loans - Past Due Financing Receivables (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	$ 4,795,012	$ 4,775,965
Nonaccrual	22,413	26,476
Total Financing Receivables	4,828,441	4,825,214
Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	7,705	19,607
Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	2,547	2,640
Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	764	526
Construction and land development
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	417,565	443,568
Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	2,162,417	2,132,066
Residential real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	1,329,166	1,324,377
Commercial and financial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	712,879	722,322
Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	206,414	202,881
Portfolio Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	3,643,035	3,557,127
Nonaccrual	15,423	15,783
Total Financing Receivables	3,667,222	3,588,251
Portfolio Loans | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	5,881	12,296
Portfolio Loans | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	2,547	2,609
Portfolio Loans | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	336	436
Portfolio Loans | Construction and land development
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	308,819	301,348
Nonaccrual	27	28
Total Financing Receivables	308,846	301,473
Portfolio Loans | 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	97
Portfolio Loans | 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 | 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 | Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	1,471,607	1,427,413
Nonaccrual	5,368	6,486
Total Financing Receivables	1,478,955	1,437,989
Portfolio Loans | Commercial real estate | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	1,016	3,852
Portfolio Loans | Commercial real estate | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	709	97
Portfolio Loans | Commercial real estate | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	255	141
Portfolio Loans | Residential real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	1,068,869	1,044,375
Nonaccrual	7,977	7,806
Total Financing Receivables	1,077,523	1,055,525
Portfolio Loans | Residential real estate | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	612	2,524
Portfolio Loans | Residential real estate | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	65	525
Portfolio Loans | Residential real estate | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	295
Portfolio Loans | Commercial and financial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	599,068	594,930
Nonaccrual	1,956	1,280
Total Financing Receivables	606,179	603,057
Portfolio Loans | Commercial and financial | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	3,724	5,186
Portfolio Loans | Commercial and financial | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	1,350	1,661
Portfolio Loans | Commercial and financial | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	81	0
Portfolio Loans | Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	194,672	189,061
Nonaccrual	95	183
Total Financing Receivables	195,719	190,207
Portfolio Loans | Consumer | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	529	637
Portfolio Loans | Consumer | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	423	326
Portfolio Loans | 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	1,141,237	1,209,670
Nonaccrual	3,942	7,096
Total Financing Receivables	1,147,431	1,222,529
PULs | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	1,824	5,642
PULs | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	31
PULs | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	428	90
PULs | Construction and land development
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	108,566	140,013
Nonaccrual	0	0
Total Financing Receivables	108,566	141,944
PULs | 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	1,931
PULs | 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 | 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 | Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	671,195	680,060
Nonaccrual	1,338	1,343
Total Financing Receivables	673,069	683,249
PULs | Commercial real estate | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	536	1,846
PULs | 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 | Commercial real estate | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
PULs | Residential real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	246,583	260,781
Nonaccrual	769	3,740
Total Financing Receivables	249,068	266,134
PULs | Residential real estate | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	1,288	1,523
PULs | 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
PULs | Residential real estate | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	428	90
PULs | Commercial and financial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	104,229	116,173
Nonaccrual	1,804	2,013
Total Financing Receivables	106,033	118,528
PULs | Commercial and financial | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	342
PULs | 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
PULs | 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
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	10,664	12,643
Nonaccrual	31	0
Total Financing Receivables	10,695	12,674
PULs | Consumer | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
PULs | Consumer | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	31
PULs | 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	10,740	9,168
Nonaccrual	3,048	3,597
Total Financing Receivables	13,788	14,434
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	1,669
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 | Construction and land development
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	138	135
Nonaccrual	15	16
Total Financing Receivables	153	151
Purchased Credit Impaired Loans | 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 | 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 | 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 | Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	9,395	8,403
Nonaccrual	998	1,391
Total Financing Receivables	10,393	10,828
Purchased Credit Impaired Loans | Commercial real estate | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, 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, Recorded Investment, 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, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Credit Impaired Loans | Residential real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	558	556
Nonaccrual	2,017	2,162
Total Financing Receivables	2,575	2,718
Purchased Credit Impaired Loans | Residential 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 | 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 | 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
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	649	74
Nonaccrual	18	28
Total Financing Receivables	667	737
Purchased Credit Impaired Loans | Commercial and financial | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, 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, Recorded Investment, 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, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Credit Impaired Loans | 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 | 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 | 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 | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	$ 0	$ 0