Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Net loss	$ (1,999,476)	$ (97,218)	$ (2,280,774)	$ (318,217)
Derivative instruments
Comprehensive income (loss) before tax	(2,527)	520	(681)	1,298
Income tax benefit (provision)	910	(187)	246	(467)
Derivatives qualifying as hedges, adjustment, net of tax	(1,617)	333	(435)	831
Pension, postretirement and other post-employment benefits
Comprehensive income (loss) before tax	1,182	(1,210)	4,950	(5,326)
Income tax benefit (provision)	(425)	435	(1,782)	1,917
Pension and other postretirement benefit plans, adjustment, net of tax	757	(775)	3,168	(3,409)
Available-for-sale securities
Comprehensive income (loss) before tax	(362)	(2,401)	(3)	(5,637)
Income tax benefit (provision)	128	864	(4)	2,029
Available-for-sale securities adjustment, net of tax	(234)	(1,537)	(7)	(3,608)
Total other comprehensive income (loss)	(1,094)	(1,979)	2,726	(6,186)
Total comprehensive loss	$ (2,000,570)	$ (99,197)	$ (2,278,048)	$ (324,403)