Subordinated Convertible Debentures (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended				1 Months Ended	3 Months Ended	12 Months Ended		3 Months Ended	12 Months Ended		1 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 QUIPS [Member]	Aug. 31, 1998 Unconsolidated Subsidiaries [Member] QUIPS [Member]	Dec. 31, 2011 Unconsolidated Subsidiaries [Member] QUIPS [Member]	Dec. 31, 2011 Unconsolidated Subsidiaries [Member] QUIPS [Member]	Jul. 31, 2008 Unconsolidated Subsidiaries [Member] QUIPS [Member]	Dec. 31, 2011 6 1/2 Subordinated Convertible Debentures [Member]	Dec. 31, 2011 6 1/2 Subordinated Convertible Debentures [Member]	Dec. 31, 2012 6 1/2 Subordinated Convertible Debentures [Member]	Aug. 31, 1998 Original Terms [Member] Unconsolidated Subsidiaries [Member] QUIPS [Member]	Jul. 31, 2008 Amended Terms [Member] Unconsolidated Subsidiaries [Member] QUIPS [Member]
Debt Instrument [Line Items]
Proceeds from issuance of private placement				$ 300	$ 300
Preferred stock, liquidation preference per share				$ 50				$ 50
Preferred stock conversion ratio												1.146	1.219
Preferred stock conversion price												$ 43.63	$ 41.02
Repurchase of common stock						32	69
Shares repurchased and retired						32	68
Extinguishment of debt										69
Gains (losses) on extinguishment of debt	(72)	(3)	(28)						1	(2)
Subordinated convertible debentures	$ 55	$ 55							$ 55	$ 55	$ 55
Stated interest rate											6.50%