Commitments And Contingencies - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2018	Dec. 31, 2015
Loss Contingencies [Line Items]
Notes Payable, Fair Value Disclosure	$ 625,000
Letters of Credit Outstanding, Amount	55,000	$ 67,000
Accounts receivable, overdue	625,086	476,903		$ 484,896
Other Nonoperating Income (Expense)	(8,788)	(6,055)	$ (6,244)
Cash repatriated	74,000
Cash and Cash Equivalents, at Carrying Value	354,259	430,316	450,193		$ 385,235
Investments and Other Noncurrent Assets	0	68,280
Derivative, Amount of Hedged Item	200,000
Fair Value Hedge Liabilities	(5,600)	(2,990)
Proceeds from Sale of Available-for-sale Securities, Debt	(69,789)	0	0
Payments to Acquire Available-for-sale Securities	10,236	10,777	39,130
Available-for-sale Securities, Debt Securities	10,000
Available-for-sale Securities, Current	10,179	0
Other Income [Member]
Loss Contingencies [Line Items]
Other Nonoperating Income (Expense)	(19,000)	(100)	$ (7,300)
Angola, Kwanza
Loss Contingencies [Line Items]
Cash and Cash Equivalents, at Carrying Value	9,309	$ 26,922
Other Noncurrent Liabilities [Member]
Loss Contingencies [Line Items]
Fair Value Hedge Liabilities	$ 5,600