Accumulated Other Comprehensive Income (Loss) (Schedule of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2016	Oct. 01, 2016	Dec. 31, 2015
Predecessor [Member]
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning balance		$ (1,815)
Unrealized gains (losses)		563	$ (8,153)
Amounts reclassified from accumulated other comprehensive income (loss)		(454)	3,097
Fresh start accounting adjustment		1,706
Ending balance			(1,815)
Predecessor [Member] | Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning balance	$ 0	(1,815)	3,241
Ending balance		0	(1,815)
Predecessor [Member] | Derivative Instruments [Member]
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning balance	0	325	2,550
Unrealized gains (losses)		(138)	3,903
Amounts reclassified from accumulated other comprehensive income (loss)		(316)	(6,128)
Fresh start accounting adjustment		129
Ending balance		0	325
Predecessor [Member] | Pension, Postretirement and Other Post-Employment Benefits [Member]
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning balance	0	(721)	2,860
Unrealized gains (losses)		0	(8,723)
Amounts reclassified from accumulated other comprehensive income (loss)		(1,363)	5,142
Fresh start accounting adjustment		2,084
Ending balance		0	(721)
Predecessor [Member] | Available-for-Sale Securities [Member]
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning balance	0	(1,419)	(2,169)
Unrealized gains (losses)		701	(3,333)
Amounts reclassified from accumulated other comprehensive income (loss)		1,225	4,083
Fresh start accounting adjustment		(507)
Ending balance		$ 0	$ (1,419)
Successor [Member]
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Unrealized gains (losses)	24,454
Amounts reclassified from accumulated other comprehensive income (loss)	0
Ending balance	24,454
Successor [Member] | Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Ending balance	24,454
Successor [Member] | Derivative Instruments [Member]
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Unrealized gains (losses)	0
Amounts reclassified from accumulated other comprehensive income (loss)	0
Ending balance	0
Successor [Member] | Pension, Postretirement and Other Post-Employment Benefits [Member]
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Unrealized gains (losses)	24,067
Amounts reclassified from accumulated other comprehensive income (loss)	0
Ending balance	24,067
Successor [Member] | Available-for-Sale Securities [Member]
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Unrealized gains (losses)	387
Amounts reclassified from accumulated other comprehensive income (loss)	0
Ending balance	$ 387