Income Taxes - Components of Net Deferred Tax Asset (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Allowance for loan losses	$ 4,014	$ 3,088
Fair value adjustments – business combination	854	966
Deferred compensation	2,405	2,056
Post-retirement benefits	754	836
Unrealized loss on interest rate swap	102	42
Nonaccrual loan interest	557	589
Accrued expenses	1,210	1,254
Deferred fees and costs	472	588
Unrealized loss on securities available for sale	0	940
Operating lease liability	4,216	0
Other	381	366
Deferred tax assets	14,965	10,725
Deferred tax liabilities:
Unrealized gain on securities available for sale	1,913	0
Premises and equipment	2,089	1,459
Unrealized gain on trading securities	340	63
Intangibles – section 197	2,305	2,414
Mortgage servicing rights	330	314
Operating lease asset	4,136	0
Other	259	178
Deferred tax liabilities	11,372	4,428
Net deferred tax asset	$ 3,593	$ 6,297