Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred Tax Assets, Gross [Abstract]
Allowance for credit losses	$ 17,616	$ 17,784
Postretirement benefits other than pensions	611	641
Alternative minimum tax credit carryforward	0	5,065
Litigation reserve	106	0
Unrealized loss on securities available for sale	3,905	1,291
Writedown of other real estate owned	1,266	1,087
Deferred compensation	1,966	2,113
Accrued interest on nonaccrual loans	1,701	1,452
Other-than-temporary impairment of securities	88	89
Depreciation of assets	0	879
Accrued incentives	2,627	1,629
Unfunded loan commitment allowance	1,452	1,557
Accrued severance	102	808
Basis difference in assets acquired	296	417
Loan origination fees and costs	290	141
Deferred rent	1,285	1,258
Other	1,084	1,105
Total deferred tax assets	34,395	37,316
Deferred tax liabilities:
Income from unconsolidated subsidiary	(623)	(619)
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	(28)	0
Other	(429)	(337)
Total deferred tax liabilities	(1,080)	(956)
Net deferred tax asset	$ 33,315	$ 36,360