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Share-Based Compensation - 2012 Equity Incentive Plan (Details) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2019 | Dec. 31, 2012
Stock options |  |
Class of Stock [Line Items] |  |
Vesting period | 4 years |
Total unrecognized compensation cost | $ 0.6 |
Weighted-average period of unvested cost | 1 year 2 months 12 days |
Restricted stock units |  |
Class of Stock [Line Items] |  |
Vesting period | 4 years |
Total unrecognized compensation cost | $ 9.3 |
Weighted-average period of unvested cost | 2 years 6 months |
Restricted stock units | Non-Management Trustees |  |
Class of Stock [Line Items] |  |
Vesting period | 1 year |
2012 Equity Incentive Plan | Stock options |  |
Class of Stock [Line Items] |  |
Expiration period | 10 years |
2012 Equity Incentive Plan | Class A common shares/units |  |
Class of Stock [Line Items] |  |
Shares available for issuance (in shares) |  | 6,000,000

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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=116856206&loc=d3e5070-113901 + Details
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