Consolidated Statements Of Equity - USD ($) shares in Thousands, $ in Millions	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Loss [Member]	Treasury Common Stock [Member]	Total
Preferred Stock Balance (in shares) at Dec. 31, 2015	19,250
Balance, beginning at Dec. 31, 2015		$ 20	$ 6,312	$ (87)	$ (353)	$ (278)	$ 5,614
Balance (in shares) at Dec. 31, 2015		79,532				(1,652)
Stock plans			(44)			$ 63	19
Stock plans (in shares)						290
Dividends on common stock			(493)				(493)
Dividends on preferred stock			(214)				(214)
Net loss				(373)			(373)
Other comprehensive income (loss), net of tax					(34)		(34)
Preferred Stock Balance (in shares) at Dec. 31, 2016	19,250
Balance, ending at Dec. 31, 2016		$ 20	5,561	(460)	(387)	$ (215)	4,519
Balance (in shares) at Dec. 31, 2016		79,532				(1,362)
Cumulative-effect adjustment and impact of adoption in accounting principle				1			1
Stock plans			(47)			$ 64	17
Stock plans (in shares)						271
Dividends on common stock			(266)				(266)
Dividends on preferred stock			(214)				(214)
Net loss				(1,804)			(1,804)
Other comprehensive income (loss), net of tax					21		21
Preferred Stock Balance (in shares) at Dec. 31, 2017	19,250
Balance, ending at Dec. 31, 2017		$ 20	5,034	(2,263)	(366)	$ (151)	$ 2,274
Balance (in shares) at Dec. 31, 2017		79,532				(1,091)	78,441
Cumulative-effect adjustment and impact of adoption in accounting principle				154			$ 154
Conversion of preferred stock, shares converted	(19,250)
Conversion of preferred stock, amount issued		$ 7	(7)
Conversion of preferred stock, shares issued		25,529
Stock plans			(118)			$ 137	19
Stock plans (in shares)		964				602
Dividends on preferred stock			(107)				(107)
Net loss				(643)			(643)
Other comprehensive income (loss), net of tax					(97)		(97)
Balance, ending at Dec. 31, 2018		$ 27	$ 4,802	$ (2,752)	$ (463)	$ (14)	$ 1,600
Balance (in shares) at Dec. 31, 2018		106,025				(489)	105,536