3.25% Cash Convertible Senior Notes (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Debt Instrument [Line Items]
Non-cash convertible debt related expense	$ 25,000,000	$ 25,000,000	$ 39,000,000
3.25% Cash Convertible Senior Notes due 2014 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	460,000,000	460,000,000		460,000,000
Contingent Interest Payable Denominator	1,000
Derivative Financial Instruments, Liabilities, Fair Value Disclosure				124,000,000
Debt Instrument Convertible Conversion Ratio Numerator	62.5216
Debt Instrument Convertible Conversion Ratio Denominator	1,000
Debt Instrument, Convertible, Conversion Price	$ 15.99
Long-term Debt, Gross				336,000,000
Non-cash convertible debt related expense	26,000,000	24,000,000	21,000,000
Debt Instrument, Convertible, Terms of Conversion Feature	We will not deliver common stock (or any other securities) upon conversion under any circumstances.
Offering Expense				14,000,000
Cash Convertible Senior Notes 3.25 Percent Due 2014 [Member]
Debt Instrument [Line Items]
Proceeds from Debt, Net of Issuance Costs				387,000,000
Warrants [Member]
Debt Instrument [Line Items]
Debt Instrument, Convertible, Conversion Price				$ 22.99
Proceeds from Issuance of Warrants				54,000,000
Option Indexed to Issuer's Equity, Strike Price				$ 25.74
Option Indexed to Issuer's Equity, Strike Price, Adjusted	$ 22.20
Debt Instrument, Convertible, Terms of Conversion Feature				The Warrants are exercisable only at expiration in equal tranches over 60 days beginning on September 2, 2014 and ending on November 26, 2014.
Adjustments to Additional Paid in Capital, Other				54,000,000
Minimum [Member] | 3.25% Cash Convertible Senior Notes due 2014 [Member]
Debt Instrument [Line Items]
Contingency Interest Payable Rate	0.25%
Maximum [Member] | 3.25% Cash Convertible Senior Notes due 2014 [Member]
Debt Instrument [Line Items]
Contingency Interest Payable Rate	0.50%
Contingent interest features of the 3.25% Notes and Debentures [Member] | Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Debt Instrument [Line Items]
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	0	0
Cash Conversion Option [Member] | Cash Convertible Senior Notes 3.25 Percent Due 2014 [Member]
Debt Instrument [Line Items]
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	105,000,000			124,000,000
Cash Conversion Option [Member] | Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Debt Instrument [Line Items]
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	105,000,000	49,000,000
Note Hedge [Member] | Cash Convertible Senior Notes 3.25 Percent Due 2014 [Member]
Debt Instrument [Line Items]
Derivative Assets	104,000,000			112,000,000
Note Hedge [Member] | Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Debt Instrument [Line Items]
Derivative Assets	104,000,000	47,000,000
Fiscal Year 2013 [Member] | 3.25% Cash Convertible Senior Notes due 2014 [Member]
Debt Instrument [Line Items]
Expected Accretion Of Debt Discount	29,000,000
Fiscal Year 2014 [Member] | 3.25% Cash Convertible Senior Notes due 2014 [Member]
Debt Instrument [Line Items]
Expected Accretion Of Debt Discount	$ 13,000,000