Financial Instruments (Narrative 2) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2011 Location Claims Cases FinancialInstitutions	Sep. 30, 2011 Long-Term Debt With Fixed Interest Rates [Member]	Dec. 31, 2010 Long-Term Debt With Fixed Interest Rates [Member]	Sep. 30, 2011 Long-Term Debt With Variable Interest Rates [Member]	Dec. 31, 2010 Long-Term Debt With Variable Interest Rates [Member]	Sep. 16, 2011 Ruby Pipeline Obligations [Member]
Derivative [Line Items]
Interest rate added to LIBOR		4.18%	4.18%
Notional amount of interest rate derivatives		$ 162	$ 184	$ 200	$ 1,300	$ 1,100
Maximum number of financial institutions with standard and poor credit rating	10