Statement of Changes in Consolidated Equity (unaudited) - USD ($) $ in Millions	Total	Preferred Class A	Preferred stock	Common stock	Additional capital	Accumulated deficit	Accumulated deficit Preferred Class A	Accumulated other comprehensive loss	Noncontrolling interests
Balance at beginning of period at Dec. 31, 2017	$ 4,924		$ 55	$ 481	$ 8,266	$ (1,248)		$ (2,644)	$ 14
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	424					424
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	483	8,310	(943)		(2,544)	14
Balance at beginning of period at Jun. 30, 2018	5,218		55	483	8,295	(1,073)		(2,556)	14
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	161					161
Other comprehensive income (J)	12							12
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	483	8,310	(943)		(2,544)	14
Balance at beginning of period at Dec. 31, 2018	5,585		55	483	8,319	(358)		(2,926)	12
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	161					161
Other comprehensive income (J)	0
Cash dividends declared:
Preferred dividends declared, value		(2)					(2)
Common share, value	(55)					(55)
Repurchase and retirement of common stock (H)	(1,100)			(52)	(1,048)
Stock-based compensation	41				41
Common stock issued: compensation plans	3			3	0
Other	4				2				2
Balance at end of period at Sep. 30, 2019	4,710		55	434	7,314	(179)		(2,928)	14
Balance at beginning of period at Jun. 30, 2019	4,866		55	440	7,484	(256)		(2,869)	12
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	95					95
Other comprehensive income (J)	(59)							(59)
Cash dividends declared:
Preferred dividends declared, value		$ (1)					$ (1)
Common share, value	(17)					(17)
Repurchase and retirement of common stock (H)	(200)			(7)	(193)
Stock-based compensation	16				16
Common stock issued: compensation plans	6			1	5
Other	4				2				2
Balance at end of period at Sep. 30, 2019	$ 4,710		$ 55	$ 434	$ 7,314	$ (179)		$ (2,928)	$ 14