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Benefit Plans - Amounts Recognized in Balance Sheet (Details) - USD ($) $ in Millions | Dec. 31, 2020 | Dec. 31, 2019
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Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |
Current liabilities | $ (2.3) | $ (2.2)
Noncurrent liabilities | (57.5) | (52.5)
Pension benefits |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |
Noncurrent assets | 12.9 | 4.3
Current liabilities | (1.6) | (1.5)
Noncurrent liabilities | (52.1) | (46.6)
Total liabilities | (40.8) | (43.8)
Other retirement benefits |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |
Noncurrent assets | 0.0 | 0.0
Current liabilities | (0.7) | (0.7)
Noncurrent liabilities | (5.4) | (5.9)
Total liabilities | $ (6.1) | $ (6.6)

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