Share-Based Compensation - Restricted Stock Grants (Details) - Restricted Stock Units - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of awards granted (in shares)	10,608	10,489	295,274	501,035
Grant Date Fair Value (in thousands)	$ 403	$ 376	$ 9,137	$ 16,708
Trustees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of awards granted (in shares)		5,982	8,517	18,267
Vesting Period		1 year	1 year	1 year
Grant Date Fair Value (in thousands)		$ 200	$ 300	$ 575
Minimum \| Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Period	1 year	1 year	1 year	1 year
Maximum \| Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Period	3 years	3 years	3 years	3 years

Share-based Compensation Arrangement By Share-based Payment Award, Equity Instruments Other Than Options, Grants In Period, Grant Date Fair Value

No definition available.

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- Definition

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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

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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).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

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- Definition

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.

+ References

No definition available.

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