Commitments and Contingencies Available Lines of Credit, Outstanding Standby Letter of Credits, and Bonds (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Oct. 18, 2019
Line of Credit Facility [Line Items]
Multicurrency revolving line of credit			$ 500,000
Net available for additional standby LOCs under sub-facility	$ 235,693	$ 235,052
Credit Facility [Member]
Line of Credit Facility [Line Items]
Multicurrency revolving line of credit	500,000	500,000
Long-term Line of Credit	0	0
Letters of Credit Outstanding, Amount	(64,307)	(64,948)
Line of Credit Facility, Remaining Borrowing Capacity	235,700
Unsecured Multicurrency Revolving Lines of Credit [Member]
Line of Credit Facility [Line Items]
Multicurrency revolving line of credit	95,687	99,201
Letters of Credit Outstanding, Amount	(24,478)	(24,966)
Short-term borrowings	0	0
Line of Credit Facility, Remaining Borrowing Capacity	71,209	74,235
Surety Bond [Member]
Line of Credit Facility [Line Items]
Unsecured surety bonds in force	146,532	162,912
Line of Credit
Line of Credit Facility [Line Items]
Long-term Line of Credit	0	0
Line of Credit Facility, Remaining Borrowing Capacity	$ 435,693	$ 435,052