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Amount, before tax, of accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.

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Amount, before tax, of accumulated other comprehensive (income) loss for cost (credit) of benefit change attributable to participants' prior service from plan amendment or plan initiation of defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

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Amount included in accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan expected to be recognized in net periodic benefit (cost) credit for fiscal year following most recent annual statement of financial position.

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Amount included in accumulated other comprehensive (income) loss for prior service cost (credit) expected to be recognized in net periodic benefit cost (credit) for fiscal year following most recent annual statement of financial position.

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Amount, before tax, of reclassification adjustment from accumulated other comprehensive (income) loss for prior service cost (credit) of defined benefit plan.

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Amount, before tax, of gain (loss) for (increase) decrease in value of benefit obligation for change in actuarial assumptions and increase (decrease) in value of plan assets from experience different from that assumed of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.

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Amount, before tax, of reclassification adjustment from accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan.

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Pension Plan and Employee Benefits, Amounts Recognized in Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Apr. 12, 2016	Dec. 31, 2016	Dec. 31, 2017
Other Postretirement Benefits Plan [Member]
Amounts in accumulated other comprehensive income to be recognized in next fiscal year [Abstract]
Future Net actuarial loss (gain)			$ (98)
Future Prior service cost (credit)			0
Amounts in accumulated other comprehensive income [Abstract]
Net actuarial loss (gain)		$ 2,292	2,779
Prior service cost (credit)		0	0
Pension Plan [Member]
Amounts in accumulated other comprehensive income to be recognized in next fiscal year [Abstract]
Future Net actuarial loss (gain)			12,267
Future Prior service cost (credit)			(71)
Amounts in accumulated other comprehensive income [Abstract]
Net actuarial loss (gain)		145,542	142,967
Prior service cost (credit)		(274)	(203)
SERP Benefits [Member]
Amounts in accumulated other comprehensive income to be recognized in next fiscal year [Abstract]
Future Net actuarial loss (gain)			2,358
Future Prior service cost (credit)			(160)
Amounts in accumulated other comprehensive income [Abstract]
Net actuarial loss (gain)		20,999	25,336
Prior service cost (credit)		(2,368)	(1,997)
Successor [Member] \| Other Postretirement Benefits Plan [Member]
Amounts recognized in other comprehensive income [Abstract]
Net actuarial loss (gain) occurring during period		2,292	437
Net actuarial loss amortized during period		0	(50)
Prior service cost (credit) amortized during period		0	0
Successor [Member] \| Pension Plan [Member]
Amounts recognized in other comprehensive income [Abstract]
Net actuarial loss (gain) occurring during period		(10,198)	7,434
Net actuarial loss amortized during period		8,138	10,008
Prior service cost (credit) amortized during period		(51)	(71)
Successor [Member] \| SERP Benefits [Member]
Amounts recognized in other comprehensive income [Abstract]
Net actuarial loss (gain) occurring during period		(1,345)	6,622
Net actuarial loss amortized during period		1,651	2,105
Prior service cost (credit) amortized during period		$ (50)	$ (190)
Predecessor [Member] \| Other Postretirement Benefits Plan [Member]
Amounts recognized in other comprehensive income [Abstract]
Net actuarial loss (gain) occurring during period	$ 0
Net actuarial loss amortized during period	181
Prior service cost (credit) amortized during period	34
Predecessor [Member] \| Pension Plan [Member]
Amounts recognized in other comprehensive income [Abstract]
Net actuarial loss (gain) occurring during period	16,056
Net actuarial loss amortized during period	2,798
Prior service cost (credit) amortized during period	(20)
Predecessor [Member] \| SERP Benefits [Member]
Amounts recognized in other comprehensive income [Abstract]
Net actuarial loss (gain) occurring during period	0
Net actuarial loss amortized during period	574
Prior service cost (credit) amortized during period	$ 17