Commitments And Contingencies - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015	Dec. 31, 2014
Loss Contingencies [Line Items]
Derivative, Amount of Hedged Item	$ 100,000		$ 100,000
Fair Value Hedge Liabilities	7,814		7,814		$ 1,909
Loans Payable to Bank	300,000		300,000		300,000
Line of Credit Facility, Amount Outstanding	0		0		0
Other income (expense), net	570	$ (9,099)	(6,823)	$ (14,883)
Cash and Cash Equivalents, at Carrying Value	441,625	271,155	441,625	271,155	385,235	$ 430,714
Other Assets, Current	110,024		110,024		$ 191,020
Other Income [Member]
Loss Contingencies [Line Items]
Other income (expense), net	700	$ (7,900)	(7,600)	$ (17,900)
Angola, Kwanza
Loss Contingencies [Line Items]
Cash and Cash Equivalents, at Carrying Value	32,000		32,000
Investments and Other Noncurrent Assets	50,000		50,000
Other Assets, Current	$ 10,000		$ 10,000