Consolidated Statements Of Equity (Deficit) - USD ($) shares in Thousands, $ in Millions	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member] Revision of Prior Period, Accounting Standards Update, Adjustment [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]	Accumulated Deficit [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]	Accumulated Deficit [Member] Cumulative Effect, Period of Adoption, Adjusted Balance [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Loss [Member] Cumulative Effect, Period of Adoption, Adjusted Balance [Member]	Accumulated Other Comprehensive Loss [Member]	Treasury Common Stock [Member]	Revision of Prior Period, Accounting Standards Update, Adjustment [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member]	Total
Balance (Accounting Standards Update 2014-09 [Member]) at Dec. 31, 2017					$ 154							$ 154
Balance at Dec. 31, 2017		$ 20	$ 5,034				$ (2,263)		$ (366)	$ (151)			$ 2,274
Balance (in shares) at Dec. 31, 2017	19,250	79,532								(1,091)
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 ($5.56 per share)			(107)										(107)
Net loss							(643)						(643)
Other comprehensive loss, net of tax									(97)				(97)
Balance (Accounting Standards Update 2014-09 [Member]) at Dec. 31, 2018				$ 11							$ 11
Balance (Accounting Standards Update 2018-02 [Member]) at Dec. 31, 2018						$ 79		$ (79)
Balance at Dec. 31, 2018		$ 27	4,802				(2,752)		(463)	$ (14)			1,600
Balance (in shares) at Dec. 31, 2018		106,025								(489)
Stock plans			13							$ 1			14
Stock plans (in shares)										(405)
Net loss							(5,911)						(5,911)
Other comprehensive loss, net of tax									(108)				(108)
Balance (Accounting Standards Update 2018-02 [Member]) at Dec. 31, 2019									(79)
Balance at Dec. 31, 2019		$ 27	4,815				(8,573)		(650)	$ (13)			(4,394)
Balance (in shares) at Dec. 31, 2019		106,025								(894)
Stock plans			2							$ (1)			1
Stock plans (in shares)										(338)
Net loss							(402)						(402)
Other comprehensive loss, net of tax									(105)				(105)
Balance at Dec. 31, 2020		$ 27	$ 4,817				$ (8,975)		$ (755)	$ (14)			$ (4,900)
Balance (in shares) at Dec. 31, 2020		106,025								(1,232)