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Retirement Plans And Postretirement Benefits (Components Of Net Postretirement Costs) (Details) - USD ($) $ in Thousands | 5 Months Ended | 6 Months Ended | 7 Months Ended | 12 Months Ended
--- | --- | --- | --- | ---
Dec. 31, 2015 | Jun. 30, 2018 | Jun. 30, 2017 | Aug. 14, 2015 | Dec. 31, 2017 | Dec. 31, 2016
Postretirement Costs |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |
Service cost |  | $ 0 | $ 1 |  |  |
Interest cost |  | 502 | 483 |  |  |
Net cost |  | $ 502 | $ 484 |  |  |
U.S. |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |
Service cost | $ 386 |  |  |  | $ 1,305 | $ 1,325
Interest cost | 2,200 |  |  |  | 5,352 | 5,744
Mark-to-market loss (gain) | 716 |  |  |  | (4,140) | (2,322)
Net cost | 1,417 |  |  |  | (2,751) | (193)
U.S. | Predecessor [Member] |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |
Service cost |  |  |  | $ 151 |  |
Interest cost |  |  |  | 854 |  |
Net cost |  |  |  | 1,005 |  |
U.S. | Postretirement Costs |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |
Interest cost | 142 |  |  |  | 333 | 360
Mark-to-market loss (gain) | (100) |  |  |  | (1,257) | (191)
Net cost | 42 |  |  |  | (924) | 169
U.S. | Postretirement Costs | Predecessor [Member] |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |
Interest cost |  |  |  | 223 |  |
Net cost |  |  |  | 223 |  |
Foreign |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |
Service cost | 281 |  |  |  | 710 | 698
Interest cost | 94 |  |  |  | 199 | 243
Mark-to-market loss (gain) | 1,843 |  |  |  | (53) | (220)
Net cost | 1,484 |  |  |  | 557 | 423
Foreign | Predecessor [Member] |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |
Service cost |  |  |  | 98 |  |
Interest cost |  |  |  | 554 |  |
Net cost |  |  |  | 640 |  |
Foreign | Postretirement Costs |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |
Service cost | 5 |  |  |  | 2 | 4
Interest cost | 289 |  |  |  | 653 | 764
Mark-to-market loss (gain) | (621) |  |  |  | 742 | (225)
Net cost | $ (327) |  |  |  | $ 1,397 | $ (450)
Foreign | Postretirement Costs | Predecessor [Member] |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |
Service cost |  |  |  | 9 |  |
Interest cost |  |  |  | 433 |  |
Net cost |  |  |  | $ 442 |  |

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