Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ (2,140)	$ (2,204)	$ 3,046
Postretirement and postemployment plans
Change in actuarial loss and other	16	228	(52)
Income tax benefit (provision) on postretirement and postemployment plans	(4)	(86)	25
Postretirement and postemployment plans, net of tax	12	142	(27)
Derivative hedges
Net unrecognized gain	61	0	1
Income tax provision on derivative hedges	(22)	0	0
Derivative hedges, net of tax	39	0	1
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	1	0	(1)
Other comprehensive income (loss)	52	142	(27)
Comprehensive income	$ (2,088)	$ (2,062)	$ 3,019