Earnings Per Share - Summary of Reconciliation of Weighted Average Common Shares (Detail) - shares	3 Months Ended	12 Months Ended
Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Basic earnings per share:
Weighted average common shares									6,641,796	6,695,721	6,757,345
Less: Average unallocated ESOP shares									(408,620)	(474,089)	(523,485)
Weighted average common shares	6,266,585	6,211,636	6,142,680	6,188,413	6,202,635	6,236,075	6,228,994	6,218,706	6,233,176	6,221,632	6,233,860
Dilutive effect of stock options									0	0	0
Weighted average common shares - diluted	6,266,585	6,211,636	6,142,680	6,188,413	6,202,635	6,236,075	6,228,994	6,218,706	6,233,176	6,221,632	6,233,860

No definition available.

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- Definition

Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

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- Definition

The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

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Number of employee stock ownership plan (ESOP) shares that have not been committed to be released determined by relating the portion of time within a reporting period that these shares have been outstanding to the total time in that period.

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This element represents the weighted average total number of shares issued throughout the period including the first (beginning balance outstanding) and last (ending balance outstanding) day of the period before considering any reductions (for instance, shares held in treasury) to arrive at the weighted average number of shares outstanding. Weighted average relates to the portion of time within a reporting period that common shares have been issued and outstanding to the total time in that period. Such concept is used in determining the weighted average number of shares outstanding for purposes of calculating earnings per share (basic).

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Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

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