Allowance for Loan Losses - Allowance for Loan Losses (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of the period	$ 14,837	$ 14,534
Total loans charged-off	411	1,109
Total loan recoveries	298	279
Net loans charged-off (recovered)	113	830
Total provision charged to operating expense	330	532
Balance at the end of the period	15,054	14,236
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off		485
Total loan recoveries	134	82
Total provision charged to operating expense	887	(332)
Commercial [Member] | Owner Occupied Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off		147
Total loan recoveries		25
Commercial [Member] | Non Owner Occupied Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off		299
Total loan recoveries	22	23
Commercial [Member] | Residential Development [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loan recoveries	2	2
Commercial [Member] | Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off		39
Total loan recoveries	110	32
Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off	51	115
Total loan recoveries	13	32
Total provision charged to operating expense	(567)	(592)
Real Estate [Member] | Residential Mortgage [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off	51	115
Total loan recoveries	13	32
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off	360	509
Total loan recoveries	151	165
Total provision charged to operating expense	10	1,456
Consumer [Member] | Direct Installment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off	25	58
Total loan recoveries	17	16
Consumer [Member] | Indirect Installment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off	285	276
Total loan recoveries	113	94
Consumer [Member] | Home Equity Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off	50	175
Total loan recoveries	$ 21	$ 55