Employee Benefit Plans (Schedule of Defined Benefit Plans Disclosures) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2016	Jun. 30, 2016	Oct. 01, 2016	Dec. 31, 2017	Dec. 31, 2015	Oct. 02, 2016
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Curtailments		$ 3,600
CHANGE IN PLAN ASSETS
Value of Plan Assets at beginning of year				$ 274,225
Value of Plan Assets at end of year	$ 274,225			255,642
Pension Benefits
CHANGE IN PLAN ASSETS
Value of Plan Assets at beginning of year				252,278
Value of Plan Assets at end of year	252,278			240,028
Successor
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Service cost	1,583			6,320
Interest cost	1,126			4,651
Successor | Pension Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligations at beginning of year	341,427			313,629
Service cost	0			0
Interest cost	2,768			11,169
Divestitures (see Note 5 to the Consolidated Financial Statements)	0			(29,097)
Settlements	(135)			(1,532)
Curtailments	0			0
Benefits paid	(11,009)			(38,197)
Other-primarily actuarial (gain) loss	(19,422)			14,126
Fresh start accounting adjustment	0			0
Benefit Obligations at end of year	313,629		$ 341,427	270,098
CHANGE IN PLAN ASSETS
Value of Plan Assets at beginning of year	292,726			274,225
Actual return on plan assets	(7,899)			39,689
Employer contributions	407			429
Benefits paid	(11,009)			(38,197)
Divestitures	0			(20,504)
Value of Plan Assets at end of year	274,225		292,726	255,642
Accrued benefit cost	(39,404)			(14,456)
ITEMS NOT YET RECOGNIZED AS A COMPONENT OF NET PERIODIC BENEFIT COST
Prior service credit (cost)				0		$ 0
Accumulated gain				16,178		6,751
Total not yet recognized as a component of net periodic benefit cost				16,178		6,751
BALANCE SHEET AMOUNTS
Current liability				(420)		(520)
Noncurrent liability				(14,036)		(38,884)
Liability, Defined Benefit Plan				(14,456)		(39,404)
Successor | Other Postretirement Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligations at beginning of year	120,311			111,867
Service cost	180			671
Interest cost	978			4,150
Divestitures (see Note 5 to the Consolidated Financial Statements)	0			0
Settlements	0			0
Curtailments	0			(520)
Benefits paid	(1,962)			(8,152)
Other-primarily actuarial (gain) loss	(7,640)			2,503
Fresh start accounting adjustment	0			0
Benefit Obligations at end of year	111,867		120,311	110,519
CHANGE IN PLAN ASSETS
Value of Plan Assets at beginning of year	0			0
Actual return on plan assets	0
Employer contributions	1,962			8,152
Benefits paid	(1,962)			(8,152)
Divestitures	0			0
Value of Plan Assets at end of year	0		0	0
Accrued benefit cost	(111,867)			(110,519)
ITEMS NOT YET RECOGNIZED AS A COMPONENT OF NET PERIODIC BENEFIT COST
Prior service credit (cost)				0		0
Accumulated gain				5,137		7,640
Total not yet recognized as a component of net periodic benefit cost				5,137		7,640
BALANCE SHEET AMOUNTS
Current liability				(8,150)		(10,422)
Noncurrent liability				(102,369)		(101,445)
Liability, Defined Benefit Plan				$ (110,519)		$ (111,867)
Predecessor
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Service cost			3,465		$ 4,282
Interest cost			3,184		3,944
Fresh start accounting adjustment			20,794
Predecessor | Pension Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligations at beginning of year	341,427	301,292	301,292
Service cost			0		9
Interest cost			9,338		14,604
Divestitures (see Note 5 to the Consolidated Financial Statements)			0
Settlements			0
Curtailments			454
Benefits paid			(8,699)
Other-primarily actuarial (gain) loss			0
Fresh start accounting adjustment			39,042
Benefit Obligations at end of year			341,427		301,292
CHANGE IN PLAN ASSETS
Value of Plan Assets at beginning of year	292,726	273,499	273,499
Actual return on plan assets			27,811
Employer contributions			115
Benefits paid			(8,699)
Divestitures			0
Value of Plan Assets at end of year			292,726		273,499
Accrued benefit cost			(48,701)
ITEMS NOT YET RECOGNIZED AS A COMPONENT OF NET PERIODIC BENEFIT COST
Prior service credit (cost)			0
Accumulated gain			0
Total not yet recognized as a component of net periodic benefit cost			0
BALANCE SHEET AMOUNTS
Current liability			(420)
Noncurrent liability			(48,281)
Liability, Defined Benefit Plan			(48,701)
Predecessor | Other Postretirement Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligations at beginning of year	120,311	103,460	103,460
Service cost			393		866
Interest cost			3,223		1,904
Divestitures (see Note 5 to the Consolidated Financial Statements)			0
Settlements			0
Curtailments			714
Benefits paid			(8,273)
Other-primarily actuarial (gain) loss			0
Benefit Obligations at end of year			120,311		103,460
CHANGE IN PLAN ASSETS
Value of Plan Assets at beginning of year	$ 0	$ 0	0
Actual return on plan assets			0
Employer contributions			8,273
Benefits paid			(8,273)
Divestitures			0
Value of Plan Assets at end of year			0		$ 0
Accrued benefit cost			(120,311)
ITEMS NOT YET RECOGNIZED AS A COMPONENT OF NET PERIODIC BENEFIT COST
Prior service credit (cost)			0
Accumulated gain			0
Total not yet recognized as a component of net periodic benefit cost			0
BALANCE SHEET AMOUNTS
Current liability			(8,352)
Noncurrent liability			(111,959)
Liability, Defined Benefit Plan			$ (120,311)