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Pension and Savings Plans Change in Benefit Obligation, Plan Assets and Funded Status of Pension Plans (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Apr. 01, 2017 | Dec. 31, 2017 | Dec. 31, 2018 | Dec. 31, 2016
Successor |  |  |  |
Amounts recognized in the consolidated balance sheets: |  |  |  |
Take-or-pay contract-based intangible recognition |  | $ 22.5 | $ 26.7 |
Successor | Pension Plan |  |  |  |
Change in benefit obligation: |  |  |  |
Accumulated postretirement benefit obligation at beginning of period |  | 936.4 | 874.6 |
Service cost |  | 1.6 | 2.3 |
Interest cost |  | 28.0 | 31.4 |
Benefits paid |  | (45.3) | (55.1) |
Actuarial gain |  | (25.3) | 57.3 |
Accumulated postretirement benefit obligation at end of period | $ 936.4 | 874.6 | 795.9 |
Fair value of plan assets at beginning of period |  | 783.1 | 776.6 |
Actual (loss) return on plan assets |  | 80.1 | (18.7) |
Employer contributions |  | 30.1 | 62.0 |
Benefits paid and administrative fees (net of Medicare Part D reimbursements) |  | (45.3) | (55.1) |
Fair value of plan assets at end of period | 783.1 | 776.6 | 764.8 |
Funded status at end of year |  | (98.0) | (31.1) |
Amounts recognized in the consolidated balance sheets: |  |  |  |
Noncurrent obligation (included in Other noncurrent liabilities) |  | (98.0) | (31.1) |
Net amount recognized |  | (98.0) | (31.1) |
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement |  | (71.4) | 0.0 |
Take-or-pay contract-based intangible recognition |  | 0.0 | 0.0 |
Defined Benefit Plan, Plan Assets, Payment for Settlement |  | (71.4) | 0.0 |
Predecessor |  |  |  |
Amounts recognized in the consolidated balance sheets: |  |  |  |
Take-or-pay contract-based intangible recognition | 0.0 |  |  | $ 0.0
Predecessor | Pension Plan |  |  |  |
Change in benefit obligation: |  |  |  |
Accumulated postretirement benefit obligation at beginning of period |  | 936.4 | 959.3 |
Service cost | 0.6 |  |  | 2.5
Interest cost | 9.7 |  |  | $ 41.5
Benefits paid | (15.0) |  |  |
Actuarial gain | 0.0 |  |  |
Accumulated postretirement benefit obligation at end of period | 936.4 | 959.3 |  |
Fair value of plan assets at beginning of period |  | 783.1 | $ 773.0 |
Actual (loss) return on plan assets | 25.1 |  |  |
Employer contributions | 0.0 |  |  |
Benefits paid and administrative fees (net of Medicare Part D reimbursements) | (15.0) |  |  |
Fair value of plan assets at end of period | 783.1 | $ 773.0 |  |
Funded status at end of year | (153.3) |  |  |
Amounts recognized in the consolidated balance sheets: |  |  |  |
Noncurrent obligation (included in Other noncurrent liabilities) | (153.3) |  |  |
Net amount recognized | (153.3) |  |  |
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement | 0.0 |  |  |
Take-or-pay contract-based intangible recognition | (18.2) |  |  |
Defined Benefit Plan, Plan Assets, Payment for Settlement | $ 0.0 |  |  |

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- Definition Amount of increase (decrease) in plan assets of defined benefit plan from actual return (loss) determined by change in fair value of plan assets adjusted for contributions, benefit payments, and other expenses. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Amount of payment to participant of defined benefit plan which decreases benefit obligation. For pension plan, payment includes, but is not limited to, pension benefits and death benefits. For other postretirement plan, payment includes, but is not limited to, prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 60 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6414203&loc=d3e39716-114964 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(6) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Amount of payment, which decreases benefit obligation of defined benefit plan, for irrevocable action relieving primary responsibility for benefit obligation and eliminating risk for obligation and assets used to effect settlement. Transaction constituting settlement includes, but is not limited to, making lump-sum cash payment to participant in exchange for their rights to receive specified benefits and purchasing nonparticipating annuity contract. Excludes decreases to benefit obligation for remeasurement due to settlement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 30 -Section 15 -Paragraph 6 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=7577095&loc=d3e8001-114927 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(10) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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