Consolidated Statements of Comprehensive Income - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income (loss) attributable to common stock		$ 4,131	$ 1,311	$ (574)
Other comprehensive income (loss) items:
Foreign currency translation gains		0	3	0
Unrealized gains (losses) on derivatives	[1]	(6)	13	(14)
Pension and postretirement gains (losses)	[2]	137	(7)	47
Reclassification of realized losses (gains) on derivatives	[3]	13	(1)	8
Other comprehensive income, net of tax		144	8	41
Comprehensive income (loss)		$ 4,275	$ 1,319	$ (533)

[1] Net of tax of $2, $(7) and $8 in 2018, 2017 and 2016, respectively.

[2] Net of tax of $(38), $4 and $(26) in 2018, 2017 and 2016, respectively. See Note 14 for additional information.

[3] Net of tax of $(4), $0 and $(4) in 2018, 2017 and 2016, respectively.