Long-Term Debt (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Long-Term Debt
Long-term debt	$ 2,595	$ 1,769
2016 Notes [Member]
Long-Term Debt
Senior Long Term Notes	500	0
2019 Notes [Member]
Long-Term Debt
Senior Long Term Notes	845	769
2020 Notes [Member]
Long-Term Debt
Senior Long Term Notes	750	750
2040 Notes [Member]
Long-Term Debt
Senior Long Term Notes	250	250
2041 Notes [Member]
Long-Term Debt
Senior Long Term Notes	$ 250	$ 0

Sum of the carrying values as of the balance sheet date of all long-term debt, which is debt initially having maturities due after one year from the balance sheet date or beyond the operating cycle, if longer, but excluding the portions thereof scheduled to be repaid within one year (current maturities) or the normal operating cycle, if longer, and after deducting unamortized discount or premiums, if any.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_LongTermDebtNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant