Loans - Impaired Loans by Class (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	$ 71,279	$ 74,740
Unpaid Principal Balance	82,919	85,264
Related Valuation Allowance	5,714	9,392
Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	38,815	32,129
Unpaid Principal Balance	44,848	38,794
Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	110,094	106,869
Unpaid Principal Balance	127,767	124,058
Related Valuation Allowance	5,714	9,392
Commercial | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	27,521	28,925
Unpaid Principal Balance	32,626	33,209
Related Valuation Allowance	1,688	3,128
Commercial | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	7,290	7,435
Unpaid Principal Balance	9,989	11,153
Commercial | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	34,811	36,360
Unpaid Principal Balance	42,615	44,362
Related Valuation Allowance	1,688	3,128
Commercial real estate | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	21,569	21,318
Unpaid Principal Balance	28,104	27,558
Related Valuation Allowance	1,486	2,102
Commercial real estate | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	25,123	20,588
Unpaid Principal Balance	28,457	23,535
Commercial real estate | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	46,692	41,906
Unpaid Principal Balance	56,561	51,093
Related Valuation Allowance	1,486	2,102
Real estate construction and land development | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	181	177
Unpaid Principal Balance	181	177
Related Valuation Allowance	7	4
Real estate construction and land development | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	78	80
Unpaid Principal Balance	78	80
Real estate construction and land development | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	259	257
Unpaid Principal Balance	259	257
Related Valuation Allowance	7	4
Residential mortgage | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	16,416	20,864
Unpaid Principal Balance	16,416	20,864
Related Valuation Allowance	1,814	3,528
Residential mortgage | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	4,800	3,252
Unpaid Principal Balance	4,800	3,252
Residential mortgage | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	21,216	24,116
Unpaid Principal Balance	21,216	24,116
Related Valuation Allowance	1,814	3,528
Consumer installment | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,041	879
Unpaid Principal Balance	1,041	879
Related Valuation Allowance	99	240
Consumer installment | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,041	879
Unpaid Principal Balance	1,041	879
Related Valuation Allowance	99	240
Home equity | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	4,551	2,577
Unpaid Principal Balance	4,551	2,577
Related Valuation Allowance	620	390
Home equity | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,524	774
Unpaid Principal Balance	1,524	774
Home equity | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	6,075	3,351
Unpaid Principal Balance	6,075	3,351
Related Valuation Allowance	$ 620	$ 390