Commitments and Contingencies - Available Lines of Credit, Outstanding Standby Letter of Credits, and Bonds (Details) - USD ($) $ in Thousands		Dec. 31, 2018	Jan. 05, 2018	Dec. 31, 2017
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	[1]	$ 500,000		$ 500,000
Long-term borrowings	[1]	0		(125,414)
Standby LOCs issued and outstanding	[1]	(40,983)		(31,881)
Net available for additional borrowings and LOCs	[1]	259,017		218,119
Unsecured Multicurrency Revolving Lines of Credit [Member]
Line of Credit Facility [Line Items]
Multicurrency revolving line of credit		108,039		110,477
Standby LOCs issued and outstanding		(19,386)		(21,030)
Short-term borrowings(2)	[2]	(2,232)		(916)
Net available for additional borrowings and LOCs		86,421		88,531
Surety Bond [Member]
Line of Credit Facility [Line Items]
Unsecured surety bonds in force		94,365		51,344
Line of Credit [Member]
Line of Credit Facility [Line Items]
Long-term borrowings		0		(125,414)
Net available for additional borrowings and LOCs	[1]	$ 459,017		$ 342,705

[1] Refer to "Note 6: Debt" for details regarding our secured credit facilities, including the refinancing of the 2015 credit facility.

[2] (2)  Short-term borrowings are included in other current liabilities on the Consolidated Balance Sheets.