Income Taxes - Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Allowance for credit losses, loans and leases	$ 15,739	$ 18,113
Deferred compensation	2,004	1,625
Actuarial adjustments on retirement benefits*	3,982	5,408
State net operating losses	6,348	5,621
Other-than-temporary impairments on equity securities	120	151
Net unrealized holding losses on securities available-for-sale and swaps	370	483
Lease liability	7,317	8,227
Deferred loan fees and costs	0	583
Other deferred tax assets	1,526	2,148
Gross deferred tax assets	37,406	42,359
Valuation allowance	(5,558)	(4,766)
Total deferred tax assets, net of valuation allowance	31,848	37,593
Deferred tax liabilities:
Mortgage servicing rights	1,671	1,370
Retirement plans	5,419	5,309
Deferred loan fees and costs	65	0
Acquisition-related fair value adjustments	1,093	1,236
Intangible assets	3,204	2,580
Accounting method change adjustment	0	385
Depreciation	1,083	888
Right of use asset	6,650	7,491
Other deferred tax liabilities	1,241	1,820
Total deferred tax liabilities	20,426	21,079
Net deferred tax assets	$ 11,422	$ 16,514