Loans - Impaired Loans by Class (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	$ 55,239	$ 78,621
Unpaid Principal Balance	62,744	87,956
Related Valuation Allowance	4,845	8,002
Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	58,887	33,256
Unpaid Principal Balance	64,014	35,824
Related Valuation Allowance	0	0
Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	114,126	111,877
Unpaid Principal Balance	126,758	123,780
Related Valuation Allowance	4,845	8,002
Commercial | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	20,683	28,897
Unpaid Principal Balance	23,249	31,655
Related Valuation Allowance	1,421	2,296
Commercial | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	17,831	8,504
Unpaid Principal Balance	19,143	9,291
Related Valuation Allowance	0	0
Commercial | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	38,514	37,401
Unpaid Principal Balance	42,392	40,946
Related Valuation Allowance	1,421	2,296
Total commercial real estate | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	17,163	28,003
Unpaid Principal Balance	22,102	34,580
Related Valuation Allowance	1,788	3,227
Total commercial real estate | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	26,591	18,080
Unpaid Principal Balance	30,339	19,861
Related Valuation Allowance	0	0
Total commercial real estate | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	43,754	46,083
Unpaid Principal Balance	52,441	54,441
Related Valuation Allowance	1,788	3,227
Real estate construction and land development | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	207	313
Unpaid Principal Balance	207	313
Related Valuation Allowance	12	14
Real estate construction and land development | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	5,740
Unpaid Principal Balance	5,807
Related Valuation Allowance	0
Real estate construction and land development | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	5,947	313
Unpaid Principal Balance	6,014	313
Related Valuation Allowance	12	14
Residential mortgage | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	13,026	15,872
Unpaid Principal Balance	13,026	15,872
Related Valuation Allowance	1,364	1,487
Residential mortgage | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	6,659	4,902
Unpaid Principal Balance	6,659	4,902
Related Valuation Allowance	0	0
Residential mortgage | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	19,685	20,774
Unpaid Principal Balance	19,685	20,774
Related Valuation Allowance	1,364	1,487
Consumer installment | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,014	966
Unpaid Principal Balance	1,014	966
Related Valuation Allowance	99	120
Consumer installment | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	0
Unpaid Principal Balance	0
Related Valuation Allowance	0
Consumer installment | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,014	966
Unpaid Principal Balance	1,014	966
Related Valuation Allowance	99	120
Home equity | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	3,146	4,570
Unpaid Principal Balance	3,146	4,570
Related Valuation Allowance	161	858
Home equity | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	2,066	1,770
Unpaid Principal Balance	2,066	1,770
Related Valuation Allowance	0	0
Home equity | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	5,212	6,340
Unpaid Principal Balance	5,212	6,340
Related Valuation Allowance	161	858
Owner-occupied | Commercial | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	13,483	17,774
Unpaid Principal Balance	16,970	21,588
Related Valuation Allowance	1,352	2,317
Owner-occupied | Commercial | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	12,786	11,351
Unpaid Principal Balance	14,436	12,631
Related Valuation Allowance	0	0
Owner-occupied | Commercial | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	26,269	29,125
Unpaid Principal Balance	31,406	34,219
Related Valuation Allowance	1,352	2,317
Non-owner occupied | Commercial | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	2,367	5,307
Unpaid Principal Balance	3,619	7,870
Related Valuation Allowance	116	316
Non-owner occupied | Commercial | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	10,884	5,977
Unpaid Principal Balance	11,896	6,438
Related Valuation Allowance	0	0
Non-owner occupied | Commercial | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	13,251	11,284
Unpaid Principal Balance	15,515	14,308
Related Valuation Allowance	116	316
Vacant land | Commercial | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,313	4,922
Unpaid Principal Balance	1,513	5,122
Related Valuation Allowance	320	594
Vacant land | Commercial | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	2,921	752
Unpaid Principal Balance	4,007	792
Related Valuation Allowance	0	0
Vacant land | Commercial | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	4,234	5,674
Unpaid Principal Balance	5,520	5,914
Related Valuation Allowance	$ 320	$ 594