Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Estimated period over which an employee is required to provide service in exchange for the equity-based payment award, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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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Number of shares authorized for issuance under share-based payment arrangement.

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Number of shares issued under share-based payment arrangement.

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Share Transactions - Share-based compensation (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 28, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted during the period, shares	63,591
General and administrative expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	$ 600,000	$ 0
Performance-vesting restricted share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted during the period, shares	63,591
Weighted average grant date fair value, per share	$ 23.00
Performance-vesting restricted share units \| Immediate vesting
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted during the period, shares	14,675
Share-based compensation, shares issued in period	10,870
Performance-vesting restricted share units \| Vesting over requisite service period
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted during the period, shares	48,916
Requisite service period	3 years
2018 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized			907,315
Number of shares available for future grant	678,437