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Share Incentive Plans - Summary of Terms of Each Retirement Eligibility Category (Details) | 12 Months Ended
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Dec. 31, 2020
Age 62 for Employees [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Eligibility | For employees hired prior to January 1, 2009 and who were age 59 or older as of February 1, 2019.
Effect on unvested restricted shares, restricted units and Options | Awards immediately vest and Options continue to be exercisable for the balance of the applicable ten-year option period.
Effect on LTI Plan | Awards are prorated in proportion to the number of days worked in the first year of the three-year performance period and the individual does not receive any payout of shares or units until the final payout is determined at the end of the three-year performance period.
Rule of 70 for Employees [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Eligibility | All employees (1).
Effect on unvested restricted shares, restricted units and Options | Awards continue to vest per the original vesting schedule, subject to certain conditions, and Options continue to be exercisable for the balance of the applicable ten-year option period.
Effect on LTI Plan | Awards are prorated in proportion to the number of days worked in the first year of the three-year performance period and the individual does not receive any payout of shares or units until the final payout is determined at the end of the three-year performance period.
Age 72 for Trustees [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Eligibility | All non-employee Trustees.
Effect on unvested restricted shares, restricted units and Options | Awards immediately vest and Options continue to be exercisable for the balance of the applicable ten-year option period.
Effect on LTI Plan | Awards are prorated in proportion to the number of days worked in the first year of the three-year performance period and the individual does not receive any payout of shares or units until the final payout is determined at the end of the three-year performance period.

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- Definition Retirement benefits effect on unvested restricted shares, restricted units and options. + References No definition available. + Details
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- Definition Description of nature of event resulting in defined benefit plan providing special or contractual termination benefits. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (q) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
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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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