Loans - Past Due Financing Receivables (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	$ 3,933,711	$ 3,788,998
Nonaccrual	26,182	19,524
Total Financing Receivables	3,974,016	3,817,377
Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	13,521	8,082
Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	109	773
Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	493	0
Portfolio Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	3,194,195	2,903,109
Nonaccrual	19,558	12,569
Total Financing Receivables	3,221,569	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	7,816	6,245
Portfolio Loans | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	686
Portfolio Loans | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Purchased Unimpaired Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	728,620	874,028
Nonaccrual	4,305	2,041
Total Financing Receivables	739,232	877,351
Purchased Unimpaired Loans | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	5,705	1,195
Purchased Unimpaired Loans | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	109	87
Purchased Unimpaired Loans | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	493	0
Purchased Credit Impaired Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	10,896	11,861
Nonaccrual	2,319	4,914
Total Financing Receivables	13,215	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
Commercial real estate | Portfolio Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	1,286,765	1,165,738
Nonaccrual	9,498	1,690
Total Financing Receivables	1,297,051	1,170,618
Commercial real estate | Portfolio Loans | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	788	2,605
Commercial real estate | Portfolio Loans | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	585
Commercial real estate | Portfolio Loans | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Commercial real estate | Purchased Unimpaired Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	390,619	457,899
Nonaccrual	408	720
Total Financing Receivables	393,366	459,598
Commercial real estate | Purchased Unimpaired Loans | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	2,339	979
Commercial real estate | Purchased Unimpaired Loans | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Commercial real estate | Purchased Unimpaired Loans | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Commercial real estate | Purchased Credit Impaired Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	9,451	9,352
Nonaccrual	1,427	424
Total Financing Receivables	10,878	9,776
Commercial real estate | 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	0
Commercial real estate | 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
Commercial real estate | 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
Commerical and financial | Portfolio Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	543,301	507,501
Nonaccrual	913	2,127
Total Financing Receivables	548,758	512,430
Commerical and financial | Portfolio Loans | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	4,544	2,776
Commerical and financial | Portfolio Loans | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	26
Commerical and financial | Portfolio Loans | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Commerical and financial | Purchased Unimpaired Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	67,366	92,315
Nonaccrual	0	321
Total Financing Receivables	69,318	92,690
Commerical and financial | Purchased Unimpaired Loans | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	1,459	54
Commerical and financial | Purchased Unimpaired Loans | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Commerical and financial | Purchased Unimpaired Loans | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	493	0
Commerical and financial | Purchased Credit Impaired Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	749	844
Nonaccrual	45	50
Total Financing Receivables	794	894
Commerical and financial | 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	0
Commerical and financial | 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
Commerical and financial | 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
Consumer | Portfolio Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	183,410	178,676
Nonaccrual	164	98
Total Financing Receivables	183,718	178,826
Consumer | Portfolio Loans | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	144	52
Consumer | Portfolio Loans | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Consumer | Portfolio Loans | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Consumer | Purchased Unimpaired Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	7,098	10,610
Nonaccrual	0	0
Total Financing Receivables	7,118	10,610
Consumer | Purchased Unimpaired Loans | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	20	0
Consumer | Purchased Unimpaired Loans | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Consumer | Purchased Unimpaired Loans | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Consumer | Purchased Credit Impaired Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	0	0
Nonaccrual	0	0
Total Financing Receivables	0	0
Consumer | 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	0
Consumer | 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
Consumer | 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
Construction and land development | Portfolio Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	250,053	215,077
Nonaccrual	217	238
Total Financing Receivables	250,314	215,315
Construction and land development | Portfolio Loans | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	44	0
Construction and land development | Portfolio Loans | 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 | Portfolio Loans | 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 | Purchased Unimpaired Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	108,017	126,655
Nonaccrual	0	0
Total Financing Receivables	108,630	126,689
Construction and land development | Purchased Unimpaired Loans | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	613	34
Construction and land development | Purchased Unimpaired Loans | 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 | Purchased Unimpaired Loans | 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 | Purchased Credit Impaired Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	126	1,121
Nonaccrual	0	0
Total Financing Receivables	126	1,121
Construction and land development | 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	0
Construction and land development | 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
Construction and land development | 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
Residential real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	1,103,945	1,038,810
Residential real estate | Portfolio Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	930,666	836,117
Nonaccrual	8,766	8,416
Total Financing Receivables	941,728	845,420
Residential real estate | Portfolio Loans | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	2,296	812
Residential real estate | Portfolio Loans | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	75
Residential real estate | Portfolio Loans | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Residential real estate | Purchased Unimpaired Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	155,520	186,549
Nonaccrual	3,897	1,000
Total Financing Receivables	160,800	187,764
Residential real estate | Purchased Unimpaired Loans | Accruing 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	1,274	128
Residential real estate | Purchased Unimpaired Loans | Accruing 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	109	87
Residential real estate | Purchased Unimpaired Loans | Accruing Greater Than 90 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Residential real estate | Purchased Credit Impaired Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	570	544
Nonaccrual	847	4,440
Total Financing Receivables	1,417	5,626
Residential real estate | 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
Residential real estate | 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
Residential real estate | 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