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Postretirement Health Care and Life Insurance Benefits Reconciliation of Postretirement Plans' Funded Status to the Balance Sheet (Details) $ in Millions | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Apr. 01, 2017 USD ($) | Dec. 31, 2017 USD ($) | Dec. 31, 2018 USD ($) years | Dec. 31, 2016 USD ($) years
Successor |  |  |  |
Change in plan assets: |  |  |  |
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), after Tax |  | $ 0.0 | $ (44.6) |
Successor | Postretirement Health Care and Life Insurance Benefits |  |  |  |
Change in benefit obligation: |  |  |  |
Accumulated postretirement benefit obligation at beginning of period |  |  | 783.3 |
Service cost |  | 6.9 | 8.2 |
Interest cost |  | 24.2 | 28.3 |
Participant contributions |  | 0.4 | 0.5 |
Plan amendments |  | 0.0 | (51.7) |
Benefits paid |  | (29.3) | (44.8) |
Actuarial gain |  | (22.0) | (128.4) |
Fresh start reporting adjustments |  | 0.0 | 0.0 |
Accumulated postretirement benefit obligation at end of period |  | 783.3 | 595.4 |
Change in plan assets: |  |  |  |
Fair value of plan assets at beginning of period |  | 0.0 | 0.0 |
Employer contributions |  | 28.9 | 59.3 |
Participant contributions |  | 0.4 | 0.5 |
Benefits paid and administrative fees (net of Medicare Part D reimbursements) |  | (29.3) | (44.8) |
Fair value of plan assets at end of period | $ 0.0 | 0.0 | 15.0 |
Funded status at end of period |  | (783.3) | (580.4) |
Less: Current portion (included in “Accounts payable and accrued expenses”) |  | 53.3 | 32.7 |
Noncurrent obligation (included in “Accrued postretirement benefit costs”) |  | (730.0) | $ (547.7) |
Remaining service period for remaining eligible employees | years |  |  | 5.9 |
Successor | Annual Benefits | Postretirement Health Care and Life Insurance Benefits |  |  |  |
Change in benefit obligation: |  |  |  |
Plan amendments |  |  | $ 50.2 |
Successor | Limitation of eligibility based on age and service criteria | Postretirement Health Care and Life Insurance Benefits |  |  |  |
Change in benefit obligation: |  |  |  |
Plan amendments |  |  | 1.5 |
Successor | Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member] |  |  |  |
Change in plan assets: |  |  |  |
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), after Tax |  | 0.0 | $ 44.6 |
Predecessor |  |  |  |
Change in plan assets: |  |  |  |
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), after Tax | 0.0 |  |  | $ 4.5
Predecessor | Postretirement Health Care and Life Insurance Benefits |  |  |  |
Change in benefit obligation: |  |  |  |
Accumulated postretirement benefit obligation at beginning of period | 812.1 | 803.1 |  |
Service cost | 2.3 |  |  | 10.4
Interest cost | 8.4 |  |  | 34.5
Participant contributions | 0.2 |  |  |
Plan amendments | 0.0 |  |  |
Benefits paid | (12.8) |  |  |
Actuarial gain | 0.0 |  |  | 0.0
Fresh start reporting adjustments | (7.1) |  |  |
Accumulated postretirement benefit obligation at end of period | 803.1 |  |  | 812.1
Change in plan assets: |  |  |  |
Fair value of plan assets at beginning of period | 0.0 | $ 0.0 |  |
Employer contributions | 12.6 |  |  |
Participant contributions | 0.2 |  |  |
Benefits paid and administrative fees (net of Medicare Part D reimbursements) | (12.8) |  |  |
Fair value of plan assets at end of period | 0.0 |  |  | $ 0.0
Funded status at end of period | (803.1) |  |  |
Less: Current portion (included in “Accounts payable and accrued expenses”) | 56.1 |  |  |
Noncurrent obligation (included in “Accrued postretirement benefit costs”) | (747.0) |  |  |
Remaining service period for remaining eligible employees | years |  |  |  | 10.3
Predecessor | Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member] |  |  |  |
Change in plan assets: |  |  |  |
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), after Tax | $ 0.0 |  |  | $ (4.5)

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