Statement of Changes in Consolidated Equity (unaudited) - USD ($) $ in Millions	Total	Preferred Class A	Preferred Class B	Preferred stock	Mandatory convertible preferred stock	Common stock	Additional capital	Accumulated deficit	Accumulated deficit Preferred Class A	Accumulated deficit Preferred Class B	Accumulated other comprehensive loss	Noncontrolling Interests
Balance at beginning of period at Dec. 31, 2016	$ 5,141			$ 55	$ 3	$ 438	$ 8,214	$ (1,027)			$ (2,568)	$ 26
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	534							534				0
Other comprehensive income (loss) (J)	114										114	0
Cash dividends declared:
Preferred dividends declared, value		$ (1)	$ (34)						$ (1)	$ (34)
Common share, value	(54)							(54)
Stock-based compensation	48						48
Common stock issued: compensation plans	3					3
Distributions	(14)											(14)
Other	16							15				1
Balance at end of period at Jun. 30, 2017	5,753			55	3	441	8,262	(567)			(2,454)	13
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	212											0
Other comprehensive income (loss) (J)	44											0
Balance at end of period at Jun. 30, 2017	5,753			55	3	441	8,262	(567)			(2,454)	13
Balance at beginning of period at Dec. 31, 2017	4,924			55	0	481	8,266	(1,248)			(2,644)	14
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	263							263				0
Other comprehensive income (loss) (J)	88										88	0
Cash dividends declared:
Preferred dividends declared, value		$ (1)							$ (1)
Common share, value	(87)							(87)
Stock-based compensation	29						29
Common stock issued: compensation plans	2					2	0
Balance at end of period at Jun. 30, 2018	5,218			55	0	483	8,295	(1,073)			(2,556)	14
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	120											0
Other comprehensive income (loss) (J)	(170)											0
Balance at end of period at Jun. 30, 2018	$ 5,218			$ 55	$ 0	$ 483	$ 8,295	$ (1,073)			$ (2,556)	$ 14