Loans - Contractual Aging of Recorded Investment in Past Due Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	$ 3,788,998	$ 2,857,695
Nonaccrual	19,524	18,071
Total Financing Receivables	3,817,377	2,879,536
Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	8,082	2,281
Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	773	1,489
Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Portfolio Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	2,903,109	2,412,629
Nonaccrual	12,569	11,023
Total Financing Receivables	2,922,609	2,425,850
Portfolio Loans [Member] | Commercial real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	1,165,738	1,039,882
Nonaccrual	1,690	1,784
Total Financing Receivables	1,170,618	1,041,915
Portfolio Loans [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	178,676	153,176
Nonaccrual	98	170
Total Financing Receivables	178,826	153,434
Portfolio Loans [Member] | Commerical and financial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	507,501	308,652
Nonaccrual	2,127	49
Total Financing Receivables	512,430	308,731
Portfolio Loans [Member] | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	6,245	1,707
Portfolio Loans [Member] | Accruing 30-59 Days Past Due | Commercial real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	2,605	78
Portfolio Loans [Member] | Accruing 30-59 Days Past Due | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	52	29
Portfolio Loans [Member] | Accruing 30-59 Days Past Due | Commerical and financial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	2,776	30
Portfolio Loans [Member] | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	686	491
Portfolio Loans [Member] | Accruing 60-89 Days Past Due | Commercial real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	585	171
Portfolio Loans [Member] | Accruing 60-89 Days Past Due | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	59
Portfolio Loans [Member] | Accruing 60-89 Days Past Due | Commerical and financial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	26	0
Portfolio Loans [Member] | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Portfolio Loans [Member] | Accruing Greater Than 90 Days | Commercial real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Portfolio Loans [Member] | Accruing Greater Than 90 Days | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Portfolio Loans [Member] | Accruing Greater Than 90 Days | Commerical and financial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Purchased Unimpaired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	874,028	436,540
Nonaccrual	2,041	2,763
Total Financing Receivables	877,351	440,690
Purchased Unimpaired Loans [Member] | Commercial real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	457,899	302,318
Nonaccrual	720	1,272
Total Financing Receivables	459,598	304,420
Purchased Unimpaired Loans [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	10,610	981
Nonaccrual	0	0
Total Financing Receivables	10,610	1,018
Purchased Unimpaired Loans [Member] | Commerical and financial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	92,315	60,353
Nonaccrual	321	197
Total Financing Receivables	92,690	60,917
Purchased Unimpaired Loans [Member] | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	1,195	574
Purchased Unimpaired Loans [Member] | Accruing 30-59 Days Past Due | Commercial real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	979	345
Purchased Unimpaired Loans [Member] | Accruing 30-59 Days Past Due | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	37
Purchased Unimpaired Loans [Member] | Accruing 30-59 Days Past Due | Commerical and financial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	54	39
Purchased Unimpaired Loans [Member] | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	87	813
Purchased Unimpaired Loans [Member] | Accruing 60-89 Days Past Due | Commercial real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	485
Purchased Unimpaired Loans [Member] | Accruing 60-89 Days Past Due | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Purchased Unimpaired Loans [Member] | Accruing 60-89 Days Past Due | Commerical and financial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	328
Purchased Unimpaired Loans [Member] | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Purchased Unimpaired Loans [Member] | Accruing Greater Than 90 Days | Commercial real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Purchased Unimpaired Loans [Member] | Accruing Greater Than 90 Days | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Purchased Unimpaired Loans [Member] | Accruing Greater Than 90 Days | Commerical and financial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	11,861	8,526
Nonaccrual	4,914	4,285
Total Financing Receivables	17,417	12,996
Purchased Credit Impaired Loans [Member] | Commercial real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	9,352	6,972
Nonaccrual	424	4,285
Total Financing Receivables	9,776	11,257
Purchased Credit Impaired Loans [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	0	0
Nonaccrual	0	0
Total Financing Receivables	0	0
Purchased Credit Impaired Loans [Member] | Commerical and financial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	844	941
Nonaccrual	50	0
Total Financing Receivables	894	941
Purchased Credit Impaired Loans [Member] | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	642	0
Purchased Credit Impaired Loans [Member] | Accruing 30-59 Days Past Due | Commercial real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Purchased Credit Impaired Loans [Member] | Accruing 30-59 Days Past Due | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Purchased Credit Impaired Loans [Member] | Accruing 30-59 Days Past Due | Commerical and financial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Purchased Credit Impaired Loans [Member] | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	185
Purchased Credit Impaired Loans [Member] | Accruing 60-89 Days Past Due | Commercial real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Purchased Credit Impaired Loans [Member] | Accruing 60-89 Days Past Due | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Purchased Credit Impaired Loans [Member] | Accruing 60-89 Days Past Due | Commerical and financial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Purchased Credit Impaired Loans [Member] | 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 [Member] | Accruing Greater Than 90 Days | Commercial real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Purchased Credit Impaired Loans [Member] | Accruing Greater Than 90 Days | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Purchased Credit Impaired Loans [Member] | Accruing Greater Than 90 Days | Commerical and financial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Construction and land development [Member] | Portfolio Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	215,077	137,042
Nonaccrual	238	438
Total Financing Receivables	215,315	137,480
Construction and land development [Member] | Portfolio Loans [Member] | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Construction and land development [Member] | Portfolio Loans [Member] | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Construction and land development [Member] | Portfolio Loans [Member] | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Construction and land development [Member] | Purchased Unimpaired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	126,655	22,490
Nonaccrual	0	32
Total Financing Receivables	126,689	22,522
Construction and land development [Member] | Purchased Unimpaired Loans [Member] | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	34	0
Construction and land development [Member] | Purchased Unimpaired Loans [Member] | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Construction and land development [Member] | Purchased Unimpaired Loans [Member] | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Construction and land development [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	1,121	114
Nonaccrual	0	0
Total Financing Receivables	1,121	114
Construction and land development [Member] | Purchased Credit Impaired Loans [Member] | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Construction and land development [Member] | Purchased Credit Impaired Loans [Member] | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Construction and land development [Member] | Purchased Credit Impaired Loans [Member] | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Residential real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	1,038,810	836,787
Residential real estate [Member] | Portfolio Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	836,117	773,877
Nonaccrual	8,416	8,582
Total Financing Receivables	845,420	784,290
Residential real estate [Member] | Portfolio Loans [Member] | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	812	1,570
Residential real estate [Member] | Portfolio Loans [Member] | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	75	261
Residential real estate [Member] | Portfolio Loans [Member] | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Residential real estate [Member] | Purchased Unimpaired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	186,549	50,398
Nonaccrual	1,000	1,262
Total Financing Receivables	187,764	51,813
Residential real estate [Member] | Purchased Unimpaired Loans [Member] | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	128	153
Residential real estate [Member] | Purchased Unimpaired Loans [Member] | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	87	0
Residential real estate [Member] | Purchased Unimpaired Loans [Member] | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Residential real estate [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	544	499
Nonaccrual	4,440	0
Total Financing Receivables	5,626	684
Residential real estate [Member] | Purchased Credit Impaired Loans [Member] | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	642	0
Residential real estate [Member] | Purchased Credit Impaired Loans [Member] | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	185
Residential real estate [Member] | Purchased Credit Impaired Loans [Member] | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	$ 0	$ 0