Loans - Impaired Loans by Class (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	$ 61,054	$ 78,621
Unpaid Principal Balance	70,437	87,956
Related Valuation Allowance	6,994	8,002
Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	50,064	33,256
Unpaid Principal Balance	53,664	35,824
Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	111,118	111,877
Unpaid Principal Balance	124,101	123,780
Related Valuation Allowance	6,994	8,002
Commercial | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	23,500	28,897
Unpaid Principal Balance	25,998	31,655
Related Valuation Allowance	1,987	2,296
Commercial | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	14,771	8,504
Unpaid Principal Balance	15,637	9,291
Commercial | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	38,271	37,401
Unpaid Principal Balance	41,635	40,946
Related Valuation Allowance	1,987	2,296
Total commercial real estate | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	19,446	28,003
Unpaid Principal Balance	26,331	34,580
Related Valuation Allowance	3,067	3,227
Total commercial real estate | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	27,411	18,080
Unpaid Principal Balance	30,078	19,861
Total commercial real estate | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	46,857	46,083
Unpaid Principal Balance	56,409	54,441
Related Valuation Allowance	3,067	3,227
Real estate construction and land development | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	164	313
Unpaid Principal Balance	164	313
Related Valuation Allowance	26	14
Real estate construction and land development | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	174
Unpaid Principal Balance	241
Real estate construction and land development | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	338	313
Unpaid Principal Balance	405	313
Related Valuation Allowance	26	14
Residential mortgage | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	13,434	15,872
Unpaid Principal Balance	13,434	15,872
Related Valuation Allowance	1,422	1,487
Residential mortgage | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	5,928	4,902
Unpaid Principal Balance	5,928	4,902
Residential mortgage | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	19,362	20,774
Unpaid Principal Balance	19,362	20,774
Related Valuation Allowance	1,422	1,487
Consumer installment | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,101	966
Unpaid Principal Balance	1,101	966
Related Valuation Allowance	206	120
Consumer installment | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	0
Unpaid Principal Balance	0
Consumer installment | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,101	966
Unpaid Principal Balance	1,101	966
Related Valuation Allowance	206	120
Home equity | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	3,409	4,570
Unpaid Principal Balance	3,409	4,570
Related Valuation Allowance	286	858
Home equity | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,780	1,770
Unpaid Principal Balance	1,780	1,770
Home equity | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	5,189	6,340
Unpaid Principal Balance	5,189	6,340
Related Valuation Allowance	286	858
Owner-occupied | Commercial | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	15,177	17,774
Unpaid Principal Balance	19,266	21,588
Related Valuation Allowance	2,510	2,317
Owner-occupied | Commercial | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	15,435	11,351
Unpaid Principal Balance	16,291	12,631
Owner-occupied | Commercial | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	30,612	29,125
Unpaid Principal Balance	35,557	34,219
Related Valuation Allowance	2,510	2,317
Non-owner occupied | Commercial | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	2,952	5,307
Unpaid Principal Balance	5,545	7,870
Related Valuation Allowance	201	316
Non-owner occupied | Commercial | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	8,122	5,977
Unpaid Principal Balance	9,135	6,438
Non-owner occupied | Commercial | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	11,074	11,284
Unpaid Principal Balance	14,680	14,308
Related Valuation Allowance	201	316
Vacant land | Commercial | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,317	4,922
Unpaid Principal Balance	1,520	5,122
Related Valuation Allowance	356	594
Vacant land | Commercial | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	3,854	752
Unpaid Principal Balance	4,652	792
Vacant land | Commercial | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	5,171	5,674
Unpaid Principal Balance	6,172	5,914
Related Valuation Allowance	$ 356	$ 594