Fair Value Measurements (Summary Of Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 488,432	$ 531,519
Marketable securities	48,006	43,638
Derivatives	1,769	29,034
Total	538,207	604,191
Derivatives	21,308	142
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	358,500	426,266
Marketable securities	48,006	38,119
Derivatives	0	0
Total	406,506	464,385
Derivatives	0	0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	129,932	105,253
Marketable securities	0	5,519
Derivatives	1,769	29,034
Total	131,701	139,806
Derivatives	21,308	142
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Marketable securities	0	0
Derivatives	0	0
Total	0	0
Derivatives	0	0
Fair Value, Measurements, Nonrecurring | Fair Value Adjustment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Repossessed inventory at the lower of cost or net realizable value	9,000	9,300
Fair Value, Measurements, Nonrecurring | Significant Other Observable Inputs (Level 2) | Estimate of Fair Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Repossessed inventory at the lower of cost or net realizable value	$ 19,600	$ 19,300