Commitments and Contingencies - Available Lines of Credit, Outstanding Standby Letter of Credits, and Bonds (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Jan. 05, 2018
Line of Credit Facility [Line Items]
Multicurrency revolving line of credit			$ 500,000
Credit Facility [Member]
Line of Credit Facility [Line Items]
Multicurrency revolving line of credit	$ 500,000	$ 500,000
Long-term borrowings	0	0
Standby LOCs issued and outstanding	(41,072)	(40,983)
Line of credit facility, remaining borrowing capacity	258,928	259,017
Unsecured Multicurrency Revolving Lines of Credit [Member]
Line of Credit Facility [Line Items]
Multicurrency revolving line of credit	107,206	108,039
Standby LOCs issued and outstanding	(25,100)	(19,386)
Short-term borrowings	(173)	(2,232)
Line of credit facility, remaining borrowing capacity	81,933	86,421
Surety Bond [Member]
Line of Credit Facility [Line Items]
Unsecured surety bonds in force	136,004	94,365
Line of Credit [Member]
Line of Credit Facility [Line Items]
Long-term borrowings	0	0
Line of credit facility, remaining borrowing capacity	$ 458,928	$ 459,017