Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Successor
Net income (loss)	$ 37,160		$ 88,828
Derivative instruments
Comprehensive income (loss) before tax	257		276
Income tax benefit (provision)	0		0
Derivatives qualifying as hedges, adjustment, net of tax	257		276
Pension, postretirement and other post-employment benefits
Comprehensive income (loss) before tax	3,154		3,154
Income tax benefit (provision)	0		0
Pension and other postretirement benefit plans, adjustment, net of tax	3,154		3,154
Available-for-sale securities
Comprehensive income (loss) before tax	0		(387)
Income tax benefit (provision)	0		0
Available-for-sale securities adjustment, net of tax	0		(387)
Total other comprehensive income (loss)	3,411		3,043
Total comprehensive income (loss)	$ 40,571		$ 91,871
Predecessor
Net income (loss)		$ (175,887)		$ (382,589)
Derivative instruments
Comprehensive income (loss) before tax		(162)		(386)
Income tax benefit (provision)		0		81
Derivatives qualifying as hedges, adjustment, net of tax		(162)		(305)
Pension, postretirement and other post-employment benefits
Comprehensive income (loss) before tax		(2,749)		(4,087)
Income tax benefit (provision)		0		481
Pension and other postretirement benefit plans, adjustment, net of tax		(2,749)		(3,606)
Available-for-sale securities
Comprehensive income (loss) before tax		504		3,407
Income tax benefit (provision)		0		(1,043)
Available-for-sale securities adjustment, net of tax		504		2,364
Total other comprehensive income (loss)		(2,407)		(1,547)
Total comprehensive income (loss)		$ (178,294)		$ (384,136)