Income Taxes - Summary of Net Deferred Tax Asset (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Allowance for loan losses	$ 11,937	$ 11,651
Stock based compensation plans	958	865
Purchase accounting fair market value adjustments	3,632	1,192
Non-accrued interest	381	256
Deferred compensation	2,444	2,142
Depreciation and amortization	0	630
Other-than-temporary impairment loss on investment securities	41	59
Federal net operating loss carryforward	875	0
Unrealized loss on pension plans	2	0
Unrealized losses on securities available for sale	0	3,162
Other, net	594	585
Gross deferred tax assets	20,864	20,542
Deferred tax liabilities:
Core deposit intangible from acquired companies	1,235	516
Undistributed income from subsidiary not consolidated for tax return purposes (REIT)	678	149
Deferred loan costs	1,461	1,418
Depreciation and amortization	750	0
Prepaid expenses	443	459
Deferred gain on securities	162	166
Unfunded pension benefits	0	17
Loss on equity securities	65	36
Unrealized gain on investment securities	884	0
Unrealized gains on hedging derivative	80	322
Other	301	270
Gross deferred tax liabilities	6,059	3,353
Net deferred tax assets	$ 14,805	$ 17,189