Guarantees, Commitments and Contingencies (Details) (Standby Letters of Credit [Member], USD $) In Millions, unless otherwise specified	Dec. 31, 2011
Standby Letters of Credit [Member]
Loss Contingencies [Line Items]
Letters of credit used to back insurance policies and other obligations	$ 15

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

No definition available.

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