Consolidated Statements Of Equity - USD ($) $ in Millions	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings (Accumulated Deficit) [Member]	Accumulated Other Comprehensive Loss [Member]	Treasury Common Stock [Member]	Total
Balance, beginning at Dec. 31, 2014		$ 17	$ 4,230	$ 109	$ (404)	$ (294)	$ 3,658
Balance (in shares) at Dec. 31, 2014		68,532,000				(1,701,000)
Issuance of stock (in shares)	19,250,000	11,000,000
Issuance of common stock		$ 3	796				799
Issuance of preferred stock			1,866				1,866
Stock plans			(4)			$ 16	12
Stock plans (in shares)						49,000
Dividends on common stock			(456)				(456)
Dividends on preferred stock			(120)				(120)
Net loss				(196)			(196)
Other comprehensive income (loss), net of tax					51		51
Preferred Stock Balance (in shares) at Dec. 31, 2015	19,250,000
Balance, ending at Dec. 31, 2015		$ 20	6,312	(87)	(353)	$ (278)	5,614
Balance (in shares) at Dec. 31, 2015		79,532,000				(1,652,000)
Stock plans			(44)			$ 63	19
Stock plans (in shares)						290,000
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	19,250,000						19,250,000
Balance, ending at Dec. 31, 2016		$ 20	5,561	(460)	(387)	$ (215)	$ 4,519
Balance (in shares) at Dec. 31, 2016		79,532,000				(1,362,000)	78,170,000
Cumulative-effect adjustment from adoption of ASU 2016-09				1			$ 1
Stock plans			(47)			$ 64	17
Stock plans (in shares)						271,000
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	19,250,000						19,250,000
Balance, ending at Dec. 31, 2017		$ 20	$ 5,034	$ (2,263)	$ (366)	$ (151)	$ 2,274
Balance (in shares) at Dec. 31, 2017		79,532,000				(1,091,000)	78,441,000