Income Taxes - Components of Net Deferred Tax Asset (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Allowance for loan losses	$ 4,799	$ 5,076
Fair value adjustments - business combination	1,661	2,466
Deferred compensation	2,443	2,238
Impaired security valuation	497	479
Net operating loss carryover	1,137	1,646
Post-retirement benefits	1,562	1,423
Unrealized loss on interest rate swap	258	331
Nonaccrual loan interest	762	598
Accrued expenses	1,072	974
Deferred fees and costs	388	40
Other	442	351
Deferred tax assets	5,021	15,622
Deferred tax liabilities:
Unrealized gain on securities available for sale	1,900	1,474
Premises and equipment	1,737	1,528
Intangibles - section 197	4,558	4,900
Mortgage servicing rights	337	299
Other	19	124
Deferred tax liabilities	8,551	8,325
Net deferred tax asset	$ 6,470	$ 7,297