Statement of Changes in Consolidated Equity (unaudited) - USD ($) $ in Millions	Total	Common Stock [Member]	Additional Capital [Member]	Retained Earnings (Deficit) [Member]	Accumulated Other Comprehensive Loss [Member]	Non-controlling Interest [Member]
Beginning Balance at Dec. 31, 2017	$ 6,968	$ 2	$ 9,590	$ 318	$ (5,182)	$ 2,240
Net (loss) income	666			199		467
Other comprehensive income (loss) (F)	205				442	(237)
Stock-based compensation	29		29
Common stock issued: compensation plans	23		23
Contributions	109					109
Distributions	(566)					(566)
Other	28		14	1		13
Ending Balance at Sep. 30, 2018	7,462	2	9,656	518	(4,740)	2,026
Beginning Balance at Jun. 30, 2018	7,245	2	9,650	524	(4,967)	2,036
Net (loss) income	195			(6)		201
Other comprehensive income (loss) (F)	182				227	(45)
Stock-based compensation	9		9
Common stock issued: compensation plans	1		1
Distributions	(181)					(181)
Other	11		(4)			15
Ending Balance at Sep. 30, 2018	7,462	2	9,656	518	(4,740)	2,026
Beginning Balance at Dec. 31, 2018	7,588	2	9,611	570	(4,565)	1,970
Net (loss) income	(498)			(822)		324
Other comprehensive income (loss) (F)	(358)				(284)	(74)
Stock-based compensation	29		29
Common stock issued: compensation plans	2		2
Contributions	41					41
Distributions	(388)					(388)
Other	(6)		(4)			(2)
Ending Balance at Sep. 30, 2019	6,410	2	9,638	(252)	(4,849)	1,871
Beginning Balance at Jun. 30, 2019	6,859	2	9,629	(31)	(4,705)	1,964
Net (loss) income	(147)			(221)		74
Other comprehensive income (loss) (F)	(228)				(144)	(84)
Stock-based compensation	8		8
Common stock issued: compensation plans	1		1
Contributions	20					20
Distributions	(102)					(102)
Other	(1)					(1)
Ending Balance at Sep. 30, 2019	$ 6,410	$ 2	$ 9,638	$ (252)	$ (4,849)	$ 1,871