Share-Based Compensation - Additional Information (Detail) - USD ($)	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 2,046,000	$ 1,822,000
Options granted (in shares)	0	0
Options exercised (in shares)	0	34,727
Exercise of stock options	$ 0	$ 307,000
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in usd per share)	$ 16.87
Share-based compensation expense	$ 165,000	$ 160,000
Granted (in shares)	13,041
Restricted Stock \| 2018 Omnibus Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost	$ 55,000
Unrecognized compensation expense, period of recognition	3 months 14 days
Restricted Stock \| 2018 Omnibus Equity Incentive Plan \| Non-Employee Directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)	13,041	13,052
Granted (in usd per share)	$ 16.87	$ 15.96
Vesting period	1 year	1 year
Share-based compensation expense	$ 220,000	$ 208,000
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in usd per share)	$ 15.37
Share-based compensation expense	$ 1,900,000	$ 1,700,000
Unrecognized compensation cost	$ 3,100,000
Unrecognized compensation expense, period of recognition	1 year 5 months 15 days
Granted (in shares)	175,869
RSUs \| 2018 Omnibus Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in usd per share)	$ 15.37	$ 16.62
Vesting period		3 years
Share-based compensation expense	$ 901,000	$ 781,000
Granted (in shares)	175,869	141,059
RSUs \| 2018 Omnibus Equity Incentive Plan \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	2 years
RSUs \| 2018 Omnibus Equity Incentive Plan \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost	$ 0

Average annual compensation cost over vesting period.

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- Definition

Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Amount of cash inflow from exercise of option under share-based payment arrangement.

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Amount of noncash expense for share-based payment arrangement.

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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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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Net number of non-option equity instruments granted to participants.

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Gross number of share options (or share units) granted during the period.

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Number of share options (or share units) exercised during the current period.

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