Components of Non-Cash Convertible Debt Related Expense (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Non Cash Convertible Debt Related Expense [Line Items]
Non-cash convertible debt related expense	$ 25	$ 25	$ 39
Convertible Note Hedge [Member]
Non Cash Convertible Debt Related Expense [Line Items]
Fair value changes related to the derivative	(57)	65	11
Cash Conversion Option [Member]
Non Cash Convertible Debt Related Expense [Line Items]
Fair value changes related to the derivative	56	(67)	(12)
3.25% Cash Convertible Senior Notes due 2014 [Member]
Non Cash Convertible Debt Related Expense [Line Items]
Debt discount accretion	26	24	21
Non-cash convertible debt related expense	26	24	21
1.00% Senior Convertible Debentures due 2027 [Member]
Non Cash Convertible Debt Related Expense [Line Items]
Debt discount accretion	$ 0	$ 3	$ 19