CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement of Comprehensive Income [Abstract]
Net Income (Loss)	$ (998)	$ (3,236)
Adjustments for derivative instruments
Reclassification of previously deferred derivative losses to (gains) losses on derivatives, net	3	2
Income taxes on reclassification of previously deferred derivative losses to (gains) losses on derivatives, net	(1)	(1)
Total adjustments for derivative instruments, net of taxes	2	1
Adjustments for pension and other postretirement plans
Net gain (loss) incurred during period	(166)	0
Income taxes on net gain (loss) incurred during period	61	0
Prior service credit (cost) incurred during period	(1)	0
Income taxes on prior service credit (cost) incurred during period	1	0
Amortization of net actuarial (gain) loss to general and administrative expense	8	13
Income taxes on amortization of net actuarial (gain) loss to general and administrative expense	(3)	(4)
Amortization of net prior service (credit) cost to general and administrative expense	(15)	0
Income taxes on amortization of net prior service (credit) cost to general and administrative expense	5	0
Total adjustments for pension and other postretirement plans, net of taxes	(110)	9
Total	(108)	10
Comprehensive Income (Loss)	(1,106)	(3,226)
Comprehensive income (loss) attributable to noncontrolling interests	36	32
Comprehensive Income (Loss) Attributable to Common Stockholders	$ (1,142)	$ (3,258)