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, 2017
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Fresh start accounting adjustment		$ 1,706
Predecessor
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Unrealized gains (losses)		563
Amounts reclassified from accumulated other comprehensive income (loss)		(454)
Predecessor | Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning balance	$ 0	(1,815)
Ending balance		0
Predecessor | Derivative Instruments
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning balance	0	325
Unrealized gains (losses)		(138)
Amounts reclassified from accumulated other comprehensive income (loss)		(316)
Fresh start accounting adjustment		129
Ending balance		0
Predecessor | Pension, Postretirement and Other Post-Employment Benefits
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning balance	0	(721)
Amounts reclassified from accumulated other comprehensive income (loss)		(1,363)
Fresh start accounting adjustment		2,084
Ending balance		0
Predecessor | Available-for-Sale Securities
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning balance	0	(1,419)
Unrealized gains (losses)		701
Amounts reclassified from accumulated other comprehensive income (loss)		1,225
Fresh start accounting adjustment		(507)
Ending balance		$ 0
Successor
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Unrealized gains (losses)	24,454		$ (3,092)
Amounts reclassified from accumulated other comprehensive income (loss)	0		(995)
Successor | Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning balance			24,454
Ending balance	24,454		20,367
Successor | Derivative Instruments
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning balance			0
Unrealized gains (losses)	0		497
Amounts reclassified from accumulated other comprehensive income (loss)	0		150
Ending balance	0		647
Successor | Pension, Postretirement and Other Post-Employment Benefits
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning balance			24,067
Unrealized gains (losses)	24,067		(3,589)
Amounts reclassified from accumulated other comprehensive income (loss)	0		(758)
Ending balance	24,067		19,720
Successor | Available-for-Sale Securities
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning balance			387
Unrealized gains (losses)	387		0
Amounts reclassified from accumulated other comprehensive income (loss)	0		(387)
Ending balance	$ 387		$ 0