Pension Plan and Employee Benefits, Unobservable Input Reconciliation (Details) - Pension Plan [Member] - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
Apr. 12, 2016	Dec. 31, 2016	Dec. 31, 2017
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation[Roll Forward]
Fair value of plan assets at beginning of year			$ 403,715
Fair value of plan assets at end of year		$ 403,715	444,089
Predecessor [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation[Roll Forward]
Fair value of plan assets at beginning of year	$ 383,532
Fair value of plan assets at end of year	398,515
Predecessor [Member] \| Real estate funds [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation[Roll Forward]
Fair value of plan assets at beginning of year	17,890
Realized gains (losses)	71
Unrealized gains (losses)	89
Purchases	26
Sales	(205)
Fair value of plan assets at end of year	17,871
Successor [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation[Roll Forward]
Fair value of plan assets at beginning of year			403,715
Fair value of plan assets at end of year	$ 398,515	403,715	444,089
Successor [Member] \| Real estate funds [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation[Roll Forward]
Fair value of plan assets at beginning of year		17,871	18,668
Realized gains (losses)		151	(2,365)
Unrealized gains (losses)		227	2,674
Purchases		570	649
Sales		(151)	(431)
Fair value of plan assets at end of year		$ 18,668	$ 19,195

Amount of decrease in plan assets from sales.

No definition available.

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- Definition

Amount, measured using unobservable inputs, of increase (decrease) in plan assets of defined benefit plan from actual return (loss) on assets sold.

+ 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 (d)(5)(iv)(02)(A)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

+ Details

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- Definition

Amount, measured using unobservable inputs, of increase (decrease) in plan assets of defined benefit plan from actual return (loss) on assets still held.

+ References

+ Details

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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- Definition

Fair value of assets that have been segregated and restricted to provide pension or postretirement benefits. Assets include, but are not limited to, stocks, bonds, other investments, earnings from investments, and contributions by the employer and employees.

+ 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)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

+ Details

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- Definition

Amount, measured using unobservable inputs, of increase (decrease) in plan assets of defined benefit plan from purchases, sales and settlements.

+ 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 (d)(5)(iv)(02)(B)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

+ Details

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- Details

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