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Employee Share-Based Incentive Compensation Plans (Tables) | 6 Months Ended
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Jun. 30, 2023
Share-Based Payment Arrangement [Abstract] |
Summary of performance shares outstanding and accrued expense for performance shares awarded under the WTM Incentive Plan | The following table presents the performance share activity for the three and six months ended June 30, 2023 and 2022 for performance shares granted under the WTM Incentive Plan:
|  | Three Months Ended June 30, |  | Six Months Ended June 30,
|  | 2023 |  | 2022 |  | 2023 |  | 2022
$ in Millions |  | Target Performance Shares Outstanding |  | Accrued Expense |  | Target Performance Shares Outstanding |  | Accrued Expense |  | Target Performance Shares Outstanding |  | Accrued Expense |  | Target Performance Shares Outstanding |  | Accrued Expense
Beginning of period |  | 37,031 |  |  | $ | 36.4 |  |  | 39,302 |  |  | $ | 21.9 |  |  | 39,449 |  |  | $ | 67.5 |  |  | 40,828 |  |  | $ | 42.2 |
Shares paid (1) |  | — |  |  | — |  |  | — |  |  | — |  |  | (13,350) |  |  | (40.8) |  |  | (14,625) |  |  | (26.4) |
New grants |  | — |  |  | — |  |  | 150 |  |  | — |  |  | 10,895 |  |  | — |  |  | 13,225 |  |  | — |
Forfeitures and cancellations (2) |  | — |  |  | (.2) |  |  | (3) |  |  | (.4) |  |  | 37 |  |  | .2 |  |  | 21 |  |  | (.1) |
Expense recognized |  | — |  |  | 8.4 |  |  | — |  |  | 19.7 |  |  | — |  |  | 17.7 |  |  | — |  |  | 25.5 |
End of period |  | 37,031 |  |  | $ | 44.6 |  |  | 39,449 |  |  | $ | 41.2 |  |  | 37,031 |  |  | $ | 44.6 |  |  | 39,449 |  |  | $ | 41.2 |
(1) WTM performance share payments in 2023 for the 2020-2022 performance cycle, which were paid in March 2023 at 200% of target. WTM performance share payments in 2022 for the 2019-2021 performance cycle, which were paid in March 2022 at 172% of target. (2) Amounts include changes in assumed forfeitures, as required under GAAP.
Share-based Compensation, Performance Shares Award Outstanding Activity | The following table presents performance shares outstanding and accrued expense for performance shares awarded under the WTM Incentive Plan as of June 30, 2023 for each performance cycle:
|  | June 30, 2023
$ in Millions |  | Target Performance Shares Outstanding |  | Accrued Expense
Performance cycle: |  |  |  |
2021 – 2023 |  | 13,475 |  |  | $ | 26.3 |
2022 – 2024 |  | 13,225 |  |  | 17.3 |
2023 – 2025 |  | 10,895 |  |  | 1.8 |
Sub-total |  | 37,595 |  |  | 45.4 |
Assumed forfeitures |  | (564) |  |  | (.8) |
Total |  | 37,031 |  |  | $ | 44.6 |
Summary of restricted shares activity | Restricted shares are grants of a specified number of common shares that generally vest at the end of a 34-month service period. The following table presents the unrecognized compensation cost associated with the outstanding restricted share awards under the WTM Incentive Plan for the three and six months ended June 30, 2023 and 2022:
|  | Three Months Ended June 30, |  | Six Months Ended June 30,
|  | 2023 |  | 2022 |  | 2023 |  | 2022
$ in Millions |  | Restricted Shares |  | Unamortized Issue Date Fair Value |  | Restricted Shares |  | Unamortized Issue Date Fair Value |  | Restricted Shares |  | Unamortized Issue Date Fair Value |  | Restricted Shares |  | Unamortized Issue Date Fair Value
Non-vested, |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Beginning of period |  | 37,595 |  |  | $ | 28.3 |  |  | 38,200 |  |  | $ | 26.5 |  |  | 38,350 |  |  | $ | 15.5 |  |  | 37,850 |  |  | $ | 15.9 |
Issued |  | — |  |  | — |  |  | 150 |  |  | .2 |  |  | 10,895 |  |  | 16.0 |  |  | 13,225 |  |  | 13.8 |
Vested |  | — |  |  | — |  |  | — |  |  | — |  |  | (11,650) |  |  | — |  |  | (12,725) |  |  | — |
Forfeited |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |
Expense recognized |  | — |  |  | (4.0) |  |  | — |  |  | (3.7) |  |  | — |  |  | (7.2) |  |  | — |  |  | (6.7) |
End of period |  | 37,595 |  |  | $ | 24.3 |  |  | 38,350 |  |  | $ | 23.0 |  |  | 37,595 |  |  | $ | 24.3 |  |  | 38,350 |  |  | $ | 23.0 |

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