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Share-Based Compensation - 2012 Equity Incentive Plan Narrative (Details) - shares | 9 Months Ended |  |
--- | --- | --- | ---
Sep. 30, 2021 | Sep. 30, 2020 | Jun. 30, 2021 | May 31, 2021
Class of Stock [Line Items] |  |  |  |
Purchase period | 6 months |  |  |
Purchase price of common stock | 85.00% |  |  |
2021 Employee Stock Purchase Plan | Class A common shares/units |  |  |  |
Class of Stock [Line Items] |  |  |  |
Number of shares available to grant (in shares) |  |  | 3,000,000 | 9,544,095
2021 Employee Stock Purchase Plan | Restricted share units | Minimum |  |  |  |
Class of Stock [Line Items] |  |  |  |
Award vesting period | 1 year | 1 year |  |
2021 Employee Stock Purchase Plan | Restricted share units | Maximum |  |  |  |
Class of Stock [Line Items] |  |  |  |
Award vesting period | 3 years | 3 years |  |
2021 Employee Stock Purchase Plan | Restricted share units | Non-Management Trustees |  |  |  |
Class of Stock [Line Items] |  |  |  |
Award vesting period | 1 year | 1 year |  |
2021 Employee Stock Purchase Plan | Performance Share Units (PSU's) |  |  |  |
Class of Stock [Line Items] |  |  |  |
Award vesting period | 3 years |  |  |
Service period | 3 years |  |  |
2021 Employee Stock Purchase Plan | Performance Share Units (PSU's) | Minimum |  |  |  |
Class of Stock [Line Items] |  |  |  |
Percentage of units expected to vest (in percent) | 0.00% |  |  |
2021 Employee Stock Purchase Plan | Performance Share Units (PSU's) | Maximum |  |  |  |
Class of Stock [Line Items] |  |  |  |
Percentage of units expected to vest (in percent) | 200.00% |  |  |

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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. + Details
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- Definition 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. + 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 + Details
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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 + Details
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- Definition 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. + 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 -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Percentage of vesting of award under share-based payment arrangement. + 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 + Details
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