Fair Value Disclosure (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Input Level 2, Fair Value
Liabilities
Long-term debt excluding capital lease obligations	$ 8,044	$ 8,352
Carrying Amount
Liabilities
Long-term debt excluding capital lease obligations	$ 7,527	$ 8,149

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

No definition available.

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