Income Taxes - Significant Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Deferred tax assets:
Loan loss reserves	$ 4,495	$ 4,452
Depreciation	655	413
Other real estate owned valuation	52	85
Tax credits carryforward		2,193
Unrealized loss on securities available for sale	1,690	241
Unrealized loss on securities held to maturity	201	217
Interest on nonaccrual loans	490	482
Net operating loss carryforward		914
Purchase accounting adjustment	260	442
Accrued bonuses	586	551
Other	131	176
Deferred tax assets	8,560	10,166
Deferred tax liabilities:
Deferred loan fees	1,476	1,145
Federal Home Loan Bank stock dividends	2,787	2,787
Mortgage servicing rights	1,453	1,401
FHLB prepayment penalty	143	307
Prepaid expenses	595	306
Deferred tax liabilities	6,454	5,946
Net deferred tax asset	$ 2,106	$ 4,220