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)	576			576
Preferred stock dividends	(67)			(67)
Share-based compensation	10	10
Other comprehensive income	31				31
Share repurchases related to employee stock-based compensation awards	(15)					(15)
Balance at at Mar. 31, 2015	15,934	21,048	1,255	(6,319)	(35)	(15)
Balance at at Dec. 31, 2015	13,439	21,100	696	(8,110)	(231)	(16)
Net income (loss)	250			250
Preferred stock dividends	(15)			(15)
Share-based compensation	17	17
Other comprehensive income	146				146
Share repurchases related to employee stock-based compensation awards	(14)					(14)
Balance at at Mar. 31, 2016	$ 13,823	$ 21,117	$ 696	$ (7,875)	$ (85)	$ (30)