Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Net loss	$ (51,421)	$ (1,999,476)	$ (434,010)	$ (2,280,774)
Derivative instruments
Comprehensive income (loss) before tax	(149)	(2,527)	(535)	(681)
Income tax benefit (provision)	0	910	81	246
Derivatives qualifying as hedges, adjustment, net of tax	(149)	(1,617)	(454)	(435)
Pension, postretirement and other post-employment benefits
Comprehensive income (loss) before tax	2,243	1,182	(1,844)	4,950
Income tax benefit (provision)	0	(425)	481	(1,782)
Pension and other postretirement benefit plans, adjustment, net of tax	2,243	757	(1,363)	3,168
Available-for-sale securities
Comprehensive income (loss) before tax	(438)	(362)	2,969	(3)
Income tax benefit (provision)	0	128	(1,043)	(4)
Available-for-sale securities adjustment, net of tax	(438)	(234)	1,926	(7)
Total other comprehensive income (loss)	1,656	(1,094)	109	2,726
Total comprehensive loss	$ (49,765)	$ (2,000,570)	$ (433,901)	$ (2,278,048)