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	Jun. 30, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	$ 14,764	$ 11,548
Loans Past Due Over 90 Days Still Accruing	391	568
Non-Performing TDRs	1,576	1,057
Performing TDRs	2,198	2,002
Total Non-Performing Loans	18,929	15,175
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	7,471	6,094
Loans Past Due Over 90 Days Still Accruing	63	208
Non-Performing TDRs	1,024	492
Performing TDRs	139	109
Total Non-Performing Loans	8,697	6,903
Commercial [Member] | Owner Occupied Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	3,694	3,413
Loans Past Due Over 90 Days Still Accruing	63
Non-Performing TDRs	389
Performing TDRs	139	109
Total Non-Performing Loans	4,285	3,522
Commercial [Member] | Non Owner Occupied Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	616	554
Non-Performing TDRs	635	492
Total Non-Performing Loans	1,251	1,046
Commercial [Member] | Development & Spec Land [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	140	68
Total Non-Performing Loans	140	68
Commercial [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	3,021	2,059
Loans Past Due Over 90 Days Still Accruing		208
Total Non-Performing Loans	3,021	2,267
Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	4,219	2,846
Loans Past Due Over 90 Days Still Accruing	77	180
Non-Performing TDRs	416	423
Performing TDRs	1,732	1,558
Total Non-Performing Loans	6,444	5,007
Real Estate [Member] | Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	4,219	2,846
Loans Past Due Over 90 Days Still Accruing	77	180
Non-Performing TDRs	416	423
Performing TDRs	1,732	1,558
Total Non-Performing Loans	6,444	5,007
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	3,074	2,608
Loans Past Due Over 90 Days Still Accruing	251	180
Non-Performing TDRs	136	142
Performing TDRs	327	335
Total Non-Performing Loans	3,788	3,265
Consumer [Member] | Direct Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	36	35
Total Non-Performing Loans	36	35
Consumer [Member] | Indirect Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	1,129	916
Loans Past Due Over 90 Days Still Accruing	156	173
Total Non-Performing Loans	1,285	1,089
Consumer [Member] | Home Equity Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	1,909	1,657
Loans Past Due Over 90 Days Still Accruing	95	7
Non-Performing TDRs	136	142
Performing TDRs	327	335
Total Non-Performing Loans	$ 2,467	$ 2,141