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Employment Benefit Plans Postretirement Health Care and Other Benefits (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Unfunded Accumulated Postretirement Benefit Obligations Determined By Company | $ 7,820 |  |
Defined Benefit Plan, Effect of One Percentage Point Increase on Accumulated Postretirement Benefit Obligation | 182 |  |
Defined Benefit Plan, Effect of One Percentage Point Increase on Service and Interest Cost Components | 11 |  |
Defined Benefit Plan, Effect of One Percentage Point Decrease on Accumulated Postretirement Benefit Obligation | 258 |  |
Defined Benefit Plan, Effect of One Percentage Point Decrease on Service and Interest Cost Components | $ 17 |  |
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate | 3.50% | 4.00% |
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months | $ 282 |  |
Defined Benefit Plan, Expected Future Benefit Payment, Year Two | 311 |  |
Defined Benefit Plan, Expected Future Benefit Payment, Year Three | 327 |  |
Defined Benefit Plan, Expected Future Benefit Payment, Year Four | 353 |  |
Defined Benefit Plan, Expected Future Benefit Payment, Year Five | 387 |  |
Defined Benefit Plan, Expected Future Benefit Payment, Five Fiscal Years Thereafter | 2,452 |  |
Defined Benefit Plan, Benefit Obligation | $ 4,112 |  |
Maximum [Member] |  |  |
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year | 5.60% |  |
Minimum [Member] |  |  |
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year | 4.50% |  |
Successor [Member] |  |  |
Postemployment Benefits, Period Expense | $ 4,164 | $ 8,846 | $ 2,570

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- Definition Weighted average rate for present value of future retirement benefits cash flows, used to determine benefit obligation of defined benefit plan. + 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 (k)(1) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan. + 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 (a) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Amount of decrease in accumulated postretirement benefit obligation from one-percentage-point decrease in assumed health care cost trend rate. + 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 (m) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Amount of decrease in service and interest cost components of net periodic postretirement benefit cost from one-percentage-point decrease in assumed health care cost trend rate. + 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 (m) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Amount of increase in service and interest cost components of net periodic postretirement benefit cost from one-percentage-point increase in assumed health care cost trend rate. + 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 (m) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Amount of benefits for defined benefit plan expected to be paid in five fiscal years after fifth fiscal year following latest fiscal year. + 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 (f) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Assumed rate, for next fiscal year, based on annual change in cost of health care cost benefits used to measure expected cost of benefits covered by defined benefit postretirement plan. Factors include, but are not limited to, estimate of health care inflation, change in health care utilization or delivery pattern, technological advances, and change in health status of participant. Excludes factors for change in composition of plan population by age and dependency status. + 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 (l) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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