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Pension and Savings Plans Changes in the Fair Value of Master Trust's Level 3 Investments (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Apr. 01, 2017 | Dec. 31, 2017 | Dec. 31, 2019 | Dec. 31, 2018
Real estate interests |  |  |  |
Summary of changes in the fair value of the Master Trust's investments |  |  |  |
Fair value of plan assets at beginning of period |  |  | $ 6.2 |
Assets Held At Reporting Date: |  |  |  |
Fair value of plan assets at end of period |  |  | 4.1 | $ 6.2
Level 3 |  |  |  |
Summary of changes in the fair value of the Master Trust's investments |  |  |  |
Fair value of plan assets at beginning of period | $ 14.1 | $ 13.8 | 6.2 | 11.8
Assets Held At Reporting Date: |  |  |  |
Realized gains | 0.6 | 0.0 | (1.0) | 2.6
Unrealized gains relatng to investments still held at the reporting date | (0.6) | 2.2 | 1.4 | (2.6)
Purchases, sales and settlements, net | (0.3) | (4.2) | (2.5) | (5.6)
Fair value of plan assets at end of period | $ 13.8 | 11.8 | 4.1 | 6.2
Level 3 | Real estate interests |  |  |  |
Summary of changes in the fair value of the Master Trust's investments |  |  |  |
Fair value of plan assets at beginning of period |  |  | 6.2 |
Assets Held At Reporting Date: |  |  |  |
Fair value of plan assets at end of period |  |  | 4.1 | 6.2
Pension Plans, Defined Benefit |  |  |  |
Summary of changes in the fair value of the Master Trust's investments |  |  |  |
Fair value of plan assets at beginning of period |  |  | 764.8 | 776.6
Assets Held At Reporting Date: |  |  |  |
Fair value of plan assets at end of period |  | $ 776.6 | $ 855.2 | $ 764.8

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