Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Tax basis of loans in excess of financial statement basis	$ 17,006	$ 16,326
Minimum liability in defined benefit plan	1,641	2,135
Deferred compensation	2,807	2,602
Write-downs and adjustments to other real estate owned and repossessed assets	9	7
Other deferred tax assets	226	224
Total deferred tax assets	21,689	21,294
Deferred tax liabilities:
Financial statement basis of fixed assets in excess of tax basis	5,870	5,644
Intangible asset amortization deductible for tax purposes, but not for financial reporting purposes	15,191	13,881
Accretion on investment securities	1,788	1,813
Pension plan contributions	1,799	1,761
Net unrealized gain on investment securities available-for-sale	11,573	27,655
Other deferred tax liabilities	83	71
Total deferred tax liabilities	36,304	50,825
Net deferred tax asset (liability)	$ (14,615)	$ (29,531)