Commitments And Contingencies - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015	Dec. 31, 2014
Loss Contingencies [Line Items]
Derivative, Amount of Hedged Item	$ 100,000
Fair Value Hedge Liabilities	6,461		$ 1,909
Loans Payable to Bank	300,000		300,000
Line of Credit Facility, Amount Outstanding	0		0
Other income (expense), net	(5,988)	$ 700
Cash and Cash Equivalents, at Carrying Value	370,853	$ 304,512	$ 385,235	$ 430,714
Other Income [Member]
Loss Contingencies [Line Items]
Other income (expense), net	7,000
Angola, Kwanza
Loss Contingencies [Line Items]
Cash and Cash Equivalents, at Carrying Value	$ 22,000