CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net Income (Loss)	$ 427	$ (641)	$ 618	$ (1,250)
Adjustments for derivative instruments
Reclassification of previously deferred derivative losses to (gains) losses on derivatives, net	1	1	2	3
Income taxes on reclassification of previously deferred derivative losses	0	0	0	(1)
Total adjustments for derivative instruments, net of taxes	1	1	2	2
Adjustments for pension and other postretirement plans
Net gain (loss) incurred during period	25	(14)	25	1
Income taxes on net gain (loss) incurred during period	(6)	5	(6)	0
Amortization of net actuarial (gain) loss to other (income) expense, net	15	29	28	100
Income taxes on amortization of net actuarial (gain) loss	(4)	(11)	(7)	(37)
Amortization of net prior service (credit) cost to other (income) expense, net	(6)	(7)	(18)	(19)
Income taxes on amortization of net prior service (credit) cost	2	3	4	7
Total adjustments for pension and other postretirement plans, net of taxes	26	5	26	52
Total	27	6	28	54
Comprehensive Income (Loss)	454	(635)	646	(1,196)
Comprehensive income (loss) attributable to noncontrolling interests	64	58	105	182
Comprehensive Income (Loss) Attributable to Common Stockholders	$ 390	$ (693)	$ 541	$ (1,378)