Condensed Consolidated Statements of Stockholders' Equity (Unaudited) (USD $) In Millions, unless otherwise specified	Total	Common stock [Member]	Additional paid-in capital [Member]	Retained earnings [Member]	Accumulated other comprehensive income (loss) [Member]	Treasury stock [Member]	Notes receivable for the issuance of common stock [Member]
Balance at Dec. 31, 2012		$ 683	$ 2,146	$ 8,774	$ 831	$ (99)	$ (21)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	250			250
Other comprehensive income (loss), net of tax	(104)				(104)
Dividends paid to common stockholders				(55)
Stock-based compensation			(8)			7
(Increase) Decrease in notes receivable from the issuance of common stock							1
Balance at Mar. 31, 2013	12,405	683	2,138	8,969	727	(92)	(20)
Balance at Dec. 31, 2013	12,651	683	2,145	9,495	442	(91)	(23)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	13			13
Other comprehensive income (loss), net of tax	250				250
Dividends paid to common stockholders				(338)
Stock-based compensation			(1)			6
(Increase) Decrease in notes receivable from the issuance of common stock							1
Balance at Mar. 31, 2014	$ 12,582	$ 683	$ 2,144	$ 9,170	$ 692	$ (85)	$ (22)