Consolidated Statement 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
Balance at Dec. 31, 2016					$ (387)
Net loss							$ (775)
Other comprehensive income, net of tax					38		38
Balance at Sep. 30, 2017					(349)
Balance at Dec. 31, 2017		$ 20	$ 5,034	$ (2,263)	(366)	$ (151)	$ 2,274
Preferred Stock Balance (in shares) at Dec. 31, 2017	19,250
Common Stock Balance (in shares) at Dec. 31, 2017		79,532				(1,091)	78,441
Impact of adoption of ASC 606 at Dec. 31, 2017				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			(127)			$ 137	10
Stock plans (in shares)		964				619
Dividends on preferred stock			(107)				(107)
Net loss				(424)			(424)
Other comprehensive income, net of tax					36		36
Balance at Sep. 30, 2018		$ 27	$ 4,793	$ (2,533)	$ (330)	$ (14)	$ 1,943
Common Stock Balance (in shares) at Sep. 30, 2018		106,025				(472)	105,553