Mandatory Convertible Preferred Stock (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Mar. 31, 2011
Class of Stock [Line Items]
Preferred Stock, Shares Issued				10,000,000
Dividends Payable, Date of Record	Dec. 14, 2012
Mandatory Convertible Preferred Stock (Textuals) [Abstract]
Mandatory convertible preferred stock, outstanding	10,000,000	10,000,000
Issue price preferred stock				$ 50.00
Mandatory convertible preferred stock, dividends on each share	5.875%
Mandatory convertible preferred stock, liquidation preference	$ 50	$ 50		$ 50.00
Preferred stock, dividend payment terms	Dividends will accrue and accumulate from the date of issuance and, to the extent that we are legally permitted to pay a dividend and the Board of Directors declares a dividend payable, we will pay dividends in cash on January 1, April 1, July 1 and October 1 of each year, commencing on July 1, 2011 and ending on April 1, 2014.
Convertible preferred stock, terms of conversion	Unless converted earlier, each share of the mandatory convertible preferred stock will automatically convert on April 1, 2014 into between 2.7454 and 3.4317 shares of common stock, depending on the market value of our common stock for the 20 consecutive trading day period ending on the third trading day prior to April 1, 2014, subject to customary anti-dilution adjustments. At any time prior to April 1, 2014, holders may elect to convert shares of the mandatory convertible preferred stock at the minimum conversion rate of 2.7454 shares of common stock, subject to customary anti-dilution adjustments. If certain fundamental changes involving the Company occur, holders of the mandatory convertible preferred stock may convert their shares into a number of shares of common stock at the fundamental change conversion rate described in our Amended Articles of Incorporation. If the Company at any time has not paid the equivalent of six full quarterly dividends on the mandatory convertible preferred stock, the Company may, at its option, cause all, but not less than all, outstanding shares of the mandatory convertible preferred stock to be automatically converted into a number of shares of our common stock based on the fundamental change conversion rate.
Preferred stock, voting rights	Except as required by law or as specifically set forth in our Amended Articles of Incorporation, the holders of the mandatory convertible preferred stock have no voting rights.
Preferred stock, dividend preference or restrictions	So long as any of the mandatory convertible preferred stock is outstanding, no dividend, except a dividend payable in shares of our common stock, or other shares ranking junior to the mandatory convertible preferred stock, may be paid or declared or any distribution be made on shares of the common stock unless all accrued and unpaid dividends on the then outstanding mandatory convertible preferred stock payable on all dividend payment dates occurring on or prior to the date of such action have been declared and paid or funds sufficient therefor set apart.
Dividends payable, date declared, day, month and year	Dec. 02, 2012
Dividends payable, amount per share	$ 0.7344
Dividends Payable, Amount	$ 7
Payments of Dividends, Preferred Stock and Preference Stock	$ 29	$ 15	$ 0
Dividends Payable, Date to be Paid	Jan. 02, 2013