Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	24,508
Weighted-average grant date fair value (in dollars per share)	$ 26.92
Number of authorized stock-based awards available for grant (in shares)	159,224
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	40,108	39,673	52,750
Unrecognized compensation cost related to nonvested restricted stock	$ 775	$ 1,243
Fair value of shares vesting during period	1,535	1,035	$ 624
Compensation expense	$ 1,545	$ 928	$ 820
Performance Based Restricted Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	10,468	5,306
Performance Based Restricted Stock Awards \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	10,468	5,306
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	15,600
Weighted-average grant date fair value (in dollars per share)	$ 27.16

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation.

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- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Fair value of options vested. Excludes equity instruments other than options, for example, but not limited to, share units, stock appreciation rights, restricted stock.

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