Loans - Summary of Portfolio Loans Individually Evaluated for Impairment by Category (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Related Allowance	$ 200			$ 200
Financing Receivable, Allowance for Credit Losses
Portfolio loans, net
Financing Receivable, Impaired [Line Items]
Provision for Loan, Lease, and Other Losses	2,332	$ 2,385	$ 1,871
Unpaid Contractual Principal Balance	26,234			26,234	$ 24,343
Recorded Investment With No Allowance	7,182			7,182	4,856
Recorded Investment With Allowance	9,862			9,862	10,831
Total Recorded Investment	17,044			17,044	15,687
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	4,314			4,314	2,579
Impaired Financing Receivable, Related Allowance	4,314			4,314	2,579
Average Recorded Investment				14,889	19,722
Financing Receivable, Allowance for Credit Losses, Write-downs	(2,595)	(1,027)	(1,035)
Financing Receivable, Allowance for Credit Losses, Recovery	148	386	1,261
Financing Receivable, Allowance for Credit Losses	41,892	42,007	40,263	41,892	38,166
Portfolio loans, net \| Commercial and industrial
Financing Receivable, Impaired [Line Items]
Provision for Loan, Lease, and Other Losses	2,569	2,852	780
Unpaid Contractual Principal Balance	20,938			20,938	20,750
Recorded Investment With No Allowance	3,266			3,266	2,321
Recorded Investment With Allowance	8,931			8,931	10,344
Total Recorded Investment	12,197			12,197	12,665
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	4,128			4,128	2,508
Impaired Financing Receivable, Related Allowance	4,128			4,128	2,508
Average Recorded Investment				10,414	16,270
Financing Receivable, Allowance for Credit Losses, Write-downs	(2,405)	(956)	(732)
Financing Receivable, Allowance for Credit Losses, Recovery	2	118	956
Financing Receivable, Allowance for Credit Losses	29,590	29,424	27,410	29,590	26,406
Portfolio loans, net \| Commercial - investor owned
Financing Receivable, Impaired [Line Items]
Provision for Loan, Lease, and Other Losses	3	5	648
Unpaid Contractual Principal Balance	1,039			1,039	560
Recorded Investment With No Allowance	770			770	422
Recorded Investment With Allowance	0			0	0
Total Recorded Investment	770			770	422
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	0			0	0
Impaired Financing Receivable, Related Allowance	0			0	0
Average Recorded Investment				657	521
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0	0
Financing Receivable, Allowance for Credit Losses, Recovery	8	10	8
Financing Receivable, Allowance for Credit Losses	4,572	4,561	4,546	4,572	3,890
Portfolio loans, net \| Commercial - owner occupied
Financing Receivable, Impaired [Line Items]
Provision for Loan, Lease, and Other Losses	(197)	340	190
Unpaid Contractual Principal Balance	1,328			1,328	487
Recorded Investment With No Allowance	826			826	0
Recorded Investment With Allowance	462			462	487
Total Recorded Investment	1,288			1,288	487
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	177			177	71
Impaired Financing Receivable, Related Allowance	177			177	71
Average Recorded Investment				1,074	490
Financing Receivable, Allowance for Credit Losses, Write-downs	(22)	0	0
Financing Receivable, Allowance for Credit Losses, Recovery	4	3	4
Financing Receivable, Allowance for Credit Losses	3,630	3,845	3,502	3,630	3,308
Portfolio loans, net \| Construction and land development
Financing Receivable, Impaired [Line Items]
Provision for Loan, Lease, and Other Losses	154	(206)	35
Unpaid Contractual Principal Balance	0			0	441
Recorded Investment With No Allowance	0			0	136
Recorded Investment With Allowance	0			0	0
Total Recorded Investment	0			0	136
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	0			0	0
Impaired Financing Receivable, Related Allowance	0			0	0
Average Recorded Investment				0	331
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0	0
Financing Receivable, Allowance for Credit Losses, Recovery	21	168	206
Financing Receivable, Allowance for Credit Losses	1,865	1,690	1,728	1,865	1,487
Portfolio loans, net \| Residential real estate
Financing Receivable, Impaired [Line Items]
Provision for Loan, Lease, and Other Losses	(187)	(573)	259
Unpaid Contractual Principal Balance	2,600			2,600	1,730
Recorded Investment With No Allowance	2,008			2,008	1,602
Recorded Investment With Allowance	469			469	0
Total Recorded Investment	2,477			2,477	1,602
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	9			9	0
Impaired Financing Receivable, Related Allowance	9			9	0
Average Recorded Investment				2,410	1,735
Financing Receivable, Allowance for Credit Losses, Write-downs	(122)	(38)	(254)
Financing Receivable, Allowance for Credit Losses, Recovery	88	59	73
Financing Receivable, Allowance for Credit Losses	1,542	1,763	2,315	1,542	2,237
Portfolio loans, net \| Consumer and other
Financing Receivable, Impaired [Line Items]
Provision for Loan, Lease, and Other Losses	(10)	(33)	(41)
Unpaid Contractual Principal Balance	329			329	375
Recorded Investment With No Allowance	312			312	375
Recorded Investment With Allowance	0			0	0
Total Recorded Investment	312			312	375
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	0			0	0
Impaired Financing Receivable, Related Allowance	0			0	0
Average Recorded Investment				334	375
Financing Receivable, Allowance for Credit Losses, Write-downs	(46)	(33)	(49)
Financing Receivable, Allowance for Credit Losses, Recovery	25	28	14
Financing Receivable, Allowance for Credit Losses	$ 693	$ 724	$ 762	$ 693	$ 838

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Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

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