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Shared-Based Payments (Summary of Share-Based Compensation Expense) (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Disclosure of Share-Based Compensation Expenses [Abstract] |  |  |
Share-based compensation expense, pre-tax | $ 23.0 | $ 23.6 | $ 22.3
Income tax benefit, including the benefit related to stock grants that vested during the year | (6.4) | (5.6) | (5.1)
Share-based Compensation Expense, Net of Tax | $ 16.6 | $ 18.0 | $ 17.2

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