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
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)
Impact of adoption of new accounting principle | Accounting Standards Update 2014-09 [Member]				154			154
Stock plans			(134)			$ 136	2
Stock plans (in shares)		835				975
Dividends on preferred stock ($5.56 per share)			(53)				(53)
Net income (loss)				20			20
Other comprehensive income, net of tax					(1)		(1)
Balance at Mar. 31, 2018		$ 20	4,847	(2,089)	(367)	$ (15)	2,396
Preferred Stock Balance (in shares) at Mar. 31, 2018	19,250
Common Stock Balance (in shares) at Mar. 31, 2018		80,367				(116)
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)
Net income (loss)							2
Other comprehensive income, net of tax					70		70
Balance at Jun. 30, 2018		$ 27	4,788	(2,107)	(296)	$ (11)	2,401
Common Stock Balance (in shares) at Jun. 30, 2018		106,025				(215)
Balance at Mar. 31, 2018		$ 20	4,847	(2,089)	(367)	$ (15)	2,396
Preferred Stock Balance (in shares) at Mar. 31, 2018	19,250
Common Stock Balance (in shares) at Mar. 31, 2018		80,367				(116)
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			2			$ 4	6
Stock plans (in shares)		129				(99)
Dividends on preferred stock ($5.56 per share)			(54)				(54)
Net income (loss)				(18)			(18)
Other comprehensive income, net of tax					71		71
Balance at Jun. 30, 2018		$ 27	4,788	(2,107)	(296)	$ (11)	2,401
Common Stock Balance (in shares) at Jun. 30, 2018		106,025				(215)
Balance at Dec. 31, 2018		$ 27	4,802	(2,752)	(463)	$ (14)	$ 1,600
Common Stock Balance (in shares) at Dec. 31, 2018		106,025				(489)	105,536
Impact of adoption of new accounting principle | Accounting Standards Update 2016-02 [Member]				11			$ 11
Impact of adoption of new accounting principle | Accounting Standards Update 2018-02 [Member]				79	(79)
Stock plans			3				3
Stock plans (in shares)						(229)
Net income (loss)				(87)			(87)
Other comprehensive income, net of tax					8		8
Balance at Mar. 31, 2019		$ 27	4,805	(2,749)	(534)	$ (14)	1,535
Common Stock Balance (in shares) at Mar. 31, 2019		106,025				(718)
Balance at Dec. 31, 2018		$ 27	4,802	(2,752)	(463)	$ (14)	$ 1,600
Common Stock Balance (in shares) at Dec. 31, 2018		106,025				(489)	105,536
Impact of adoption of new accounting principle | Accounting Standards Update 2016-02 [Member]							$ 11
Impact of adoption of new accounting principle | Accounting Standards Update 2018-02 [Member]					(79)		(79)
Net income (loss)							(5,404)
Other comprehensive income, net of tax					17		17
Balance at Jun. 30, 2019		$ 27	4,806	(8,067)	(525)	$ (12)	$ (3,771)
Common Stock Balance (in shares) at Jun. 30, 2019		106,025				(650)	105,375
Balance at Mar. 31, 2019		$ 27	4,805	(2,749)	(534)	$ (14)	$ 1,535
Common Stock Balance (in shares) at Mar. 31, 2019		106,025				(718)
Stock plans			1			$ 2	3
Stock plans (in shares)						68
Net income (loss)				(5,317)			(5,317)
Other comprehensive income, net of tax					9		9
Balance at Jun. 30, 2019		$ 27	$ 4,806	$ (8,067)	$ (525)	$ (12)	$ (3,771)
Common Stock Balance (in shares) at Jun. 30, 2019		106,025				(650)	105,375