CONSOLIDATED STATEMENT OF CHANGES IN EQUITY (UNAUDITED) - USD ($) $ in Millions		Total	Preferred stock	Common stock	Additional paid-in capital	Accumulated deficit	Accumulated other comprehensive income (loss)	Adjustments for New Accounting Principle, Early Adoption [Member] Accumulated deficit	Adjustments for New Accounting Principle, Early Adoption [Member] Accumulated other comprehensive income (loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect adjustment to initially apply new accounting guidance | Accounting Standards Update 2016-01 [Member]								$ 0	$ 0
Cumulative effect adjustment to initially apply new accounting guidance | Accounting Standards Update 2016-09 [Member]								0
Balance at beginning of period (As Previously Reported [Member]) at Dec. 31, 2015						$ (18,199)	$ 14
Balance at beginning of period at Dec. 31, 2015			$ 1,575	$ 0	$ 23,245	(18,199)	14
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Redemption of Series B preferred stock			(575)
Dividends on preferred stock					(63)
Employee benefit plans, including transfers and other					1
Net income (loss)		$ (208)				(208)
Other comprehensive income (loss)		12					12
Total equity at end of period at Jun. 30, 2016		5,802	1,000	0	23,183	(18,407)	26
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total common shareholder's equity at end of period		4,802
Cumulative effect adjustment to initially apply new accounting guidance	[1]	(19)
Cumulative effect adjustment to initially apply new accounting guidance | Accounting Standards Update 2016-01 [Member]								19	$ (19)
Cumulative effect adjustment to initially apply new accounting guidance | Accounting Standards Update 2016-09 [Member]								$ 4
Total common shareholder's equity at end of period		4,434
Balance at beginning of period (As Previously Reported [Member]) at Dec. 31, 2016						(18,728)	24
Balance at beginning of period at Dec. 31, 2016		5,434	1,000	0	23,138	(18,705)	5
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Redemption of Series B preferred stock			0
Dividends on preferred stock					(43)
Employee benefit plans, including transfers and other					(2)
Net income (loss)		437				437
Other comprehensive income (loss)		(15)					(15)
Total equity at end of period at Jun. 30, 2017		5,815	$ 1,000	$ 0	$ 23,093	$ (18,268)	$ (10)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total common shareholder's equity at end of period		$ 4,815

[1] For information on the adoption of new accounting guidance related to fair value option debt attributable to our credit spreads, see Note 13, "New Accounting Pronouncements."