Guarantees (Details 1) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Guarantees [Abstract]
Letters of credit	$ 241,022	$ 234,482
Surety bonds	$ 104,632	$ 99,831

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