Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2016	Oct. 01, 2016	Dec. 31, 2015	Dec. 31, 2014
Predecessor [Member]
Net income (loss)		$ 1,242,081	$ (2,913,142)	$ (558,353)
Derivative instruments
Comprehensive income (loss) before tax		(532)	(3,477)	3,102
Income tax benefit (provision)		80	1,252	(1,117)
Derivatives Qualifying as Hedges, Adjustment, Net of Tax		(452)	(2,225)	1,985
Pension, postretirement and other post-employment benefits
Comprehensive income (loss) before tax		(1,848)	(5,592)	(44,143)
Income tax benefit (provision)		483	2,011	15,891
Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax		(1,365)	(3,581)	(28,252)
Available-for-sale securities
Comprehensive income (loss) before tax		2,968	1,185	(12,788)
Income tax benefit (provision)		(1,042)	(435)	4,604
Available-for-sale Securities Adjustment, Net of Tax		1,926	750	(8,184)
Total other comprehensive income (loss)		109	(5,056)	(34,451)
Total comprehensive income (loss)		$ 1,242,190	$ (2,918,198)	$ (592,804)
Successor [Member]
Net income (loss)	$ 33,449
Derivative instruments
Comprehensive income (loss) before tax	0
Income tax benefit (provision)	0
Derivatives Qualifying as Hedges, Adjustment, Net of Tax	0
Pension, postretirement and other post-employment benefits
Comprehensive income (loss) before tax	24,067
Income tax benefit (provision)	0
Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	24,067
Available-for-sale securities
Comprehensive income (loss) before tax	387
Income tax benefit (provision)	0
Available-for-sale Securities Adjustment, Net of Tax	387
Total other comprehensive income (loss)	24,454
Total comprehensive income (loss)	$ 57,903