Non-performing Loans and Impaired Loans - Non-accrual, Loans Past Due Over 90 Days Still on Accrual, and Troubled Debt Restructured ("TDRs") by Class of Loans (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	$ 6,944	$ 7,936
Loans Past Due Over 90 Days Still Accruing	245	241
Non-Performing TDRs	998	1,014
Performing TDRs	1,647	1,492
Total Non-Performing Loans	9,834	10,683
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	1,380	2,249
Loans Past Due Over 90 Days Still Accruing	150	183
Total Non-Performing Loans	1,530	2,432
Commercial [Member] | Owner Occupied Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	760	1,532
Loans Past Due Over 90 Days Still Accruing		183
Total Non-Performing Loans	760	1,715
Commercial [Member] | Non Owner Occupied Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	387	440
Total Non-Performing Loans	387	440
Commercial [Member] | Development & Spec Land Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	112	118
Total Non-Performing Loans	112	118
Commercial [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	121	159
Loans Past Due Over 90 Days Still Accruing	150
Total Non-Performing Loans	271	159
Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	2,904	2,959
Non-Performing TDRs	797	809
Performing TDRs	1,356	1,254
Total Non-Performing Loans	5,057	5,022
Real Estate [Member] | Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	2,904	2,959
Non-Performing TDRs	567	576
Performing TDRs	1,356	1,254
Total Non-Performing Loans	4,827	4,789
Real Estate [Member] | Residential Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Performing TDRs	230	233
Total Non-Performing Loans	230	233
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	2,660	2,728
Loans Past Due Over 90 Days Still Accruing	95	58
Non-Performing TDRs	201	205
Performing TDRs	291	238
Total Non-Performing Loans	3,247	3,229
Consumer [Member] | Direct Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	489	512
Total Non-Performing Loans	489	512
Consumer [Member] | Indirect Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	690	659
Loans Past Due Over 90 Days Still Accruing	69	49
Total Non-Performing Loans	759	708
Consumer [Member] | Home Equity Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	1,481	1,557
Loans Past Due Over 90 Days Still Accruing	26	9
Non-Performing TDRs	201	205
Performing TDRs	291	238
Total Non-Performing Loans	$ 1,999	$ 2,009