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Employee Share-Based Incentive Compensation Plans - Performance Shares Granted (Details) - Performance Shares - USD ($) $ in Millions | Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
--- | --- | --- | --- | ---
Share-based compensation arrangement by share-based payment award |  |  |  |
Number of nonvested options before forfeitures (in shares) | 41,450 |  |  |
Incentive compensation payable before forfeitures | $ 42.8 |  |  |
Assumed forfeitures (in shares) | (622) |  |  |
Assumed forfeitures | $ (0.6) |  |  |
Shares outstanding (in shares) | 40,828 | 42,458 | 42,473 | 40,616
Accrued incentive compensation | $ 42.2 | $ 56.3 | $ 43.7 | $ 31.7
2019 – 2021 |  |  |  |
Share-based compensation arrangement by share-based payment award |  |  |  |
Number of nonvested options before forfeitures (in shares) | 14,625 |  |  |
Incentive compensation payable before forfeitures | $ 25.3 |  |  |
2020 – 2022 |  |  |  |
Share-based compensation arrangement by share-based payment award |  |  |  |
Number of nonvested options before forfeitures (in shares) | 13,350 |  |  |
Incentive compensation payable before forfeitures | $ 15.4 |  |  |
2021 – 2023 |  |  |  |
Share-based compensation arrangement by share-based payment award |  |  |  |
Number of nonvested options before forfeitures (in shares) | 13,475 |  |  |
Incentive compensation payable before forfeitures | $ 2.1 |  |  |

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- Definition Aggregate carrying value as of the balance sheet date of liabilities for incentive compensation arrangements. + References No definition available. + Details
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- Definition Carrying value as of the balance sheet date for performance shares before forfeitures. + References No definition available. + Details
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- Definition This element represents the number of non-vested performance shares before forfeiture assumptions. + References No definition available. + Details
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