Loans - Impaired Loans by Class (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	$ 78,211	$ 78,621
Unpaid Principal Balance	84,663	87,956
Related Valuation Allowance	5,074	8,002
Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	61,239	33,256
Unpaid Principal Balance	65,374	35,824
Related Valuation Allowance	0	0
Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	139,450	111,877
Unpaid Principal Balance	150,037	123,780
Related Valuation Allowance	5,074	8,002
Commercial | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	13,394	28,897
Unpaid Principal Balance	16,109	31,655
Related Valuation Allowance	1,110	2,296
Commercial | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	25,021	8,504
Unpaid Principal Balance	26,427	9,291
Related Valuation Allowance	0	0
Commercial | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	38,415	37,401
Unpaid Principal Balance	42,536	40,946
Related Valuation Allowance	1,110	2,296
Total commercial real estate | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	18,595	28,003
Unpaid Principal Balance	22,332	34,580
Related Valuation Allowance	1,796	3,227
Total commercial real estate | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	25,872	18,080
Unpaid Principal Balance	28,534	19,861
Related Valuation Allowance	0	0
Total commercial real estate | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	44,467	46,083
Unpaid Principal Balance	50,866	54,441
Related Valuation Allowance	1,796	3,227
Real estate construction and land development | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	28,575	313
Unpaid Principal Balance	28,575	313
Related Valuation Allowance	650	14
Real estate construction and land development | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	140
Unpaid Principal Balance	207
Related Valuation Allowance	0
Real estate construction and land development | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	28,715	313
Unpaid Principal Balance	28,782	313
Related Valuation Allowance	650	14
Residential mortgage | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	12,879	15,872
Unpaid Principal Balance	12,879	15,872
Related Valuation Allowance	1,146	1,487
Residential mortgage | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	7,988	4,902
Unpaid Principal Balance	7,988	4,902
Related Valuation Allowance	0	0
Residential mortgage | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	20,867	20,774
Unpaid Principal Balance	20,867	20,774
Related Valuation Allowance	1,146	1,487
Consumer installment | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,071	966
Unpaid Principal Balance	1,071	966
Related Valuation Allowance	117	120
Consumer installment | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	475
Unpaid Principal Balance	475
Related Valuation Allowance	0
Consumer installment | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,546	966
Unpaid Principal Balance	1,546	966
Related Valuation Allowance	117	120
Home equity | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	3,697	4,570
Unpaid Principal Balance	3,697	4,570
Related Valuation Allowance	255	858
Home equity | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,743	1,770
Unpaid Principal Balance	1,743	1,770
Related Valuation Allowance	0	0
Home equity | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	5,440	6,340
Unpaid Principal Balance	5,440	6,340
Related Valuation Allowance	255	858
Owner-occupied | Commercial | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	13,278	17,774
Unpaid Principal Balance	15,607	21,588
Related Valuation Allowance	1,281	2,317
Owner-occupied | Commercial | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	10,852	11,351
Unpaid Principal Balance	11,490	12,631
Related Valuation Allowance	0	0
Owner-occupied | Commercial | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	24,130	29,125
Unpaid Principal Balance	27,097	34,219
Related Valuation Allowance	1,281	2,317
Non-owner occupied | Commercial | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	3,187	5,307
Unpaid Principal Balance	4,595	7,870
Related Valuation Allowance	142	316
Non-owner occupied | Commercial | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	12,161	5,977
Unpaid Principal Balance	13,099	6,438
Related Valuation Allowance	0	0
Non-owner occupied | Commercial | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	15,348	11,284
Unpaid Principal Balance	17,694	14,308
Related Valuation Allowance	142	316
Vacant land | Commercial | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	2,130	4,922
Unpaid Principal Balance	2,130	5,122
Related Valuation Allowance	373	594
Vacant land | Commercial | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	2,859	752
Unpaid Principal Balance	3,945	792
Related Valuation Allowance	0	0
Vacant land | Commercial | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	4,989	5,674
Unpaid Principal Balance	6,075	5,914
Related Valuation Allowance	$ 373	$ 594