Consolidated Statement Of Changes In Equity - USD ($) $ in Millions	Total	Common stock and paid-in capital [Member]	Preferred stock [Member]	Accumulated deficit [Member]	Accumulated other comprehensive (loss) income [Member]	Treasury stock [Member]
Balance at at Dec. 31, 2014	$ 15,399	$ 21,038	$ 1,255	$ (6,828)	$ (66)	$ 0
Net income (loss)	758			758
Preferred stock dividends	(1,318)			(1,318)
Stock Repurchased During Period, Value	(325)		(325)
Preferred stock redemption	(117)		(117)
Share-based compensation	31	31
Other comprehensive income	(117)				(117)
Share repurchases related to employee stock-based compensation awards	(16)					(16)
Balance at at Jun. 30, 2015	14,295	21,069	813	(7,388)	(183)	(16)
Stock Repurchase and Redemption Premium	1,193
Balance at at Dec. 31, 2015	13,439	21,100	696	(8,110)	(231)	(16)
Net income (loss)	610			610
Preferred stock dividends	(30)			(30)
Stock Repurchased During Period, Value	696		696
Share-based compensation	36	36
Other comprehensive income	266				266
Share repurchases related to employee stock-based compensation awards	(14)					(14)
Balance at at Jun. 30, 2016	$ 13,611	$ 21,136	$ 0	$ (7,530)	$ 35	$ (30)