Commitments and Contingencies (Guarantees, Surety Bonds and Letters of Credit) (Narrative) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011
Purchased surety bonds	$ 151
Standby Letters of Credit
Authorized standby letters of credit with financial institutions	36
Third Party and Equity Method Investee
Loss Contingency, Estimate of Possible Loss	82
Exposure under guarantees	$ 49