Commitments and Contingencies Available Lines of Credit, Outstanding Standby Letter of Credits, and Bonds (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Mar. 25, 2020	Dec. 31, 2019	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	$ 33,225		$ 258,928
Credit Facility [Member]
Line of Credit Facility [Line Items]
Multicurrency revolving line of credit	500,000		500,000
Long-term Line of Credit	(400,000)		0
Letters of Credit Outstanding, Amount	(66,775)		(41,072)
Unsecured Multicurrency Revolving Lines of Credit [Member]
Line of Credit Facility [Line Items]
Multicurrency revolving line of credit	103,357		107,206
Letters of Credit Outstanding, Amount	(24,021)		(25,100)
Short-term borrowings	(559)		(173)
Line of Credit Facility, Remaining Borrowing Capacity	78,777		81,933
Surety Bond [Member]
Line of Credit Facility [Line Items]
Unsecured surety bonds in force	162,324		136,004
Line of Credit [Member]
Line of Credit Facility [Line Items]
Long-term Line of Credit	(400,000)	$ (400,000)	0
Line of Credit Facility, Remaining Borrowing Capacity	$ 33,225		$ 458,928