Commitments and Contingencies Available Lines of Credit, Outstanding Standby Letter of Credits, and Bonds (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2012 Credit Facility [Member]		Dec. 31, 2011 Credit Facility [Member]		Mar. 31, 2012 Unsecured Multicurrency Revolving Lines of Credit [Member]	Dec. 31, 2011 Unsecured Multicurrency Revolving Lines of Credit [Member]	Apr. 02, 2012 Line of Credit [Member] 2011 Senior Secured Credit Facility [Member]	Mar. 31, 2012 Line of Credit [Member] 2011 Senior Secured Credit Facility [Member]
Line of Credit Facility [Line Items]
Multicurrency revolving line of credit			$ 500,000	[1]	$ 500,000	[1]	$ 62,968	$ 67,968	$ 660,000	$ 500,000
Line of Credit Facility, Amount Outstanding			(150,000)	[1]	(160,000)	[1]				150,000
Standby letters of credit issued and outstanding			(46,786)	[1]	(44,549)	[1]	(27,305)	(28,733)		46,800
Net available for additional borrowings and lines of credit			303,214	[1]	295,451	[1]	35,663	39,235		303,200
Unsecured Surety Bonds In Force	$ 151,213	$ 139,954

[1] See Note 6 for details regarding our secured credit facilities.