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	653							653				0
Other comprehensive income (J)	241										241	0
Cash dividends declared:
Preferred dividends declared, value		$ (2)	$ (51)						$ (2)	$ (51)
Common share, value	(107)							(107)
Stock-based compensation	59						59
Common stock issued: compensation plans	25					4	21
Distributions	(14)											(14)
Other	16							15				1
Balance at end of period at Sep. 30, 2017	5,961			55	3	442	8,294	(519)			(2,327)	13
Balance at beginning 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	119							119				0
Other comprehensive income (J)	127										127	0
Cash dividends declared:
Preferred dividends declared, value		(1)	$ (17)						(1)	$ (17)
Common share, value	(53)							(53)
Stock-based compensation	11						11
Common stock issued: compensation plans	22					1	21
Balance at end of period at Sep. 30, 2017	5,961			55	3	442	8,294	(519)			(2,327)	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	424							424				0
Other comprehensive income (J)	100										100	0
Cash dividends declared:
Preferred dividends declared, value		(2)							(2)
Common share, value	(117)							(117)
Stock-based compensation	43						43
Common stock issued: compensation plans	3					2	1
Balance at end of period at Sep. 30, 2018	5,375			55	0	483	8,310	(943)			(2,544)	14
Balance at beginning 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	161							161				0
Other comprehensive income (J)	12										12	0
Cash dividends declared:
Preferred dividends declared, value		$ (1)							$ (1)
Common share, value	(30)							(30)
Stock-based compensation	14						14
Common stock issued: compensation plans	1						1
Balance at end of period at Sep. 30, 2018	$ 5,375			$ 55	$ 0	$ 483	$ 8,310	$ (943)			$ (2,544)	$ 14