Pension and Other Postretirement Benefit Plans - Reconciliation of Net Postretirement Health and Life Amounts Recognized in Consolidated Balance Sheet (Details) - Postretirement Health and Life [Member] - USD ($) $ in Millions |
Dec. 31, 2019 |
Dec. 31, 2018 |
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|---|---|---|---|---|
| Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] | ||||
| Net Loss | [1] | $ (16.0) | $ (25.0) | |
| Prior Service Credit | 36.3 | 4.6 | ||
| Accumulated Net Periodic Benefit Cost in Excess of Contributions | 3.6 | (1.3) | ||
| Total Net Postretirement Health and Life Amounts Recognized in Consolidated Balance Sheet | $ 23.9 | $ (21.7) | ||
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