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)	444			444
Other comprehensive income (loss), net of tax	(705)				(705)
Dividends paid to common stockholders				(108)
Stock Issued During Period, Value, Share-based Compensation, Net of Forfeitures			(6)			8
(Increase) Decrease in notes receivable from the issuance of common stock							(3)
Balance at Jun. 30, 2013	11,944	683	2,140	9,110	126	(91)	(24)
Balance at Dec. 31, 2013	12,651	683	2,145	9,495	442	(91)	(23)
Decrease (increase) in notes receivable for common stock							22
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	280			280
Other comprehensive income (loss), net of tax	520				520
Dividends paid to common stockholders				(406)
Stock Issued During Period, Value, Share-based Compensation, Net of Forfeitures			1			6
Balance at Jun. 30, 2014	$ 13,074	$ 683	$ 2,146	$ 9,369	$ 962	$ (85)	$ (1)