Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Comprehensive Income [Abstract]
Net income	$ (2,204)	$ 3,046	$ 1,753
Postretirement and postemployment plans
Change in actuarial loss and other	228	(52)	300
Income tax benefit (provision) on postretirement and postemployment plans	(86)	25	(112)
Postretirement and postemployment plans, net of tax	142	(27)	188
Derivative hedges
Net unrecognized gain	0	1	1
Income tax provision on derivative hedges	0	0	0
Derivative hedges, net of tax	0	1	1
Foreign currency translation and other
Unrealized gain (loss)	0	0	(3)
Income tax benefit (provision) on foreign currency translation and other	0	(1)	1
Foreign currency translation and other, net of tax	0	(1)	(2)
Other comprehensive income (loss)	142	(27)	187
Comprehensive income	$ (2,062)	$ 3,019	$ 1,940