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Employee Share-Based Incentive Compensation Plans - Performance Shares (Details) - Performance Share - W T M Incentive Plan - USD ($) $ in Millions | 1 Months Ended | 3 Months Ended | 6 Months Ended | 36 Months Ended
--- | --- | --- | --- | ---
Mar. 31, 2023 | Mar. 31, 2022 | Jun. 30, 2023 | Jun. 30, 2022 | Jun. 30, 2023 | Jun. 30, 2022 | Dec. 31, 2021
Target Performance Shares Outstanding |  |  |  |  |  |  |
Beginning of period (in shares) |  |  | 37,031 | 39,302 | 39,449 | 40,828 |
Shares paid (in shares) |  |  | 0 | 0 | (13,350) | (14,625) |
New grants (in shares) |  |  | 0 | 150 | 10,895 | 13,225 | 750
Forfeitures and cancellations (in shares) |  |  | 0 | (3) | 37 | 21 |
Expense recognized (in shares) |  |  | 0 | 0 | 0 | 0 |
End of period (in shares) | 37,031 | 39,302 | 37,031 | 39,449 | 37,031 | 39,449 | 40,828
Accrued Expense |  |  |  |  |  |  |
Beginning of period |  |  | $ 36.4 | $ 21.9 | $ 67.5 | $ 42.2 |
Shares paid |  |  | 0.0 | 0.0 | (40.8) | (26.4) |
New grants |  |  | 0.0 | 0.0 | 0.0 | 0.0 |
Forfeitures and cancellations |  |  | (0.2) | (0.4) | 0.2 | (0.1) |
Expense recognized |  |  | 8.4 | 19.7 | 17.7 | 25.5 |
End of period | $ 36.4 | $ 21.9 | $ 44.6 | $ 41.2 | $ 44.6 | $ 41.2 | $ 42.2
Range Of Performance Cycle Current Year |  |  |  |  |  |  |
Accrued Expense |  |  |  |  |  |  |
Percentage of target payout - minimum actual | 200.00% |  |  |  |  |  |
Range Of Performance Cycle Previous Year |  |  |  |  |  |  |
Accrued Expense |  |  |  |  |  |  |
Percentage of target payout - minimum actual |  | 172.00% |  |  |  |  |

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- Definition Amount of expense for award under share-based payment arrangement. Excludes amount capitalized. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 718 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 14.F) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479830/718-10-S99-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 718 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (h)(1)(i) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480429/718-10-50-2 + Details
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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://www.xbrl.org/2003/role/disclosureRef -Topic 718 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(01) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480429/718-10-50-2 + Details
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- Definition The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 718 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (c)(2)(i) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480429/718-10-50-2 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 718 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (c)(2)(ii) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480429/718-10-50-2 + Details
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- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
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- Definition The total reduction to unamortized compensation cost for performance shares forfeited during the period. + References No definition available. + Details
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- Definition The amount of performance shares that were paid out (including deposits into a deferred compensation plan) or that expired due to failure to meet performance criteria. + References No definition available. + Details
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