Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (170)	$ (386)	$ (577)	$ (662)
Postretirement and postemployment plans
Change in actuarial loss and other	19	86	(5)	162
Income tax benefit (provision) on postretirement and postemployment plans	(7)	(30)	2	(57)
Postretirement and postemployment plans, net of tax	12	56	(3)	105
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	(2)	0	(2)	0
Other comprehensive income (loss)	10	56	(5)	105
Comprehensive income (loss)	$ (160)	$ (330)	$ (582)	$ (557)