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)	716			716
Other comprehensive income (loss), net of tax	(718)				(718)
Dividends paid to common stockholders				(162)
Stock-based compensation			(4)			8
Decrease (increase) in notes receivable for common stock							(1)
Balance at Sep. 30, 2013	12,153	683	2,142	9,328	113	(91)	(22)
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)	493			493
Other comprehensive income (loss), net of tax	331				331
Dividends paid to common stockholders				(473)
Stock-based compensation			4			6
Decrease (increase) in notes receivable for common stock							22
Balance at Sep. 30, 2014	$ 13,034	$ 683	$ 2,149	$ 9,515	$ 773	$ (85)	$ (1)