CONSOLIDATED STATEMENT OF CHANGES IN EQUITY - USD ($) $ in Millions	Total	Preferred stock	Common stock	Additional paid-in capital	Accumulated deficit	Accumulated other comprehensive income (loss)
Balance at beginning of period at Dec. 31, 2013		$ 1,575	$ 0	$ 23,485	$ (18,291)	$ (108)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Redemption of Series B preferred stock		0
Dividends on preferred stock				(123)
Employee benefit plans, including transfers and other				19
Net income (loss)	$ 523				523
Other comprehensive income	43					43
Total equity at end of period at Dec. 31, 2014	7,123	$ 1,575	$ 0	23,381	(17,768)	(65)
Number of shares at beginning of period at Dec. 31, 2013		576,000	68
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Number of shares of Series B preferred stock redeemed		0
Number of shares at end of period at Dec. 31, 2014		576,000	68
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total common shareholder's equity at end of period	5,548
Redemption of Series B preferred stock		$ 0
Dividends on preferred stock				(123)
Employee benefit plans, including transfers and other				(13)
Net income (loss)	(431)				(431)
Other comprehensive income	79					79
Total equity at end of period at Dec. 31, 2015	6,635	$ 1,575	$ 0	23,245	(18,199)	14
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Number of shares of Series B preferred stock redeemed		0
Number of shares at end of period at Dec. 31, 2015		576,000	68
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total common shareholder's equity at end of period	5,060
Redemption of Series B preferred stock		$ (575)
Dividends on preferred stock				(106)
Employee benefit plans, including transfers and other				(1)
Net income (loss)	(529)				(529)
Other comprehensive income	10					10
Total equity at end of period at Dec. 31, 2016	5,434	$ 1,000	$ 0	$ 23,138	$ (18,728)	$ 24
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Number of shares of Series B preferred stock redeemed		(575,000)
Number of shares at end of period at Dec. 31, 2016		1,000	68
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total common shareholder's equity at end of period	$ 4,434