Guarantees (Details 1) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Letters of credit and surety bonds outstanding
Letters of credit	$ 196,671	$ 188,499
Surety bonds	$ 74,280	$ 76,273

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