Description Of Business And Basis Of Presentation (Schedule of New Accounting Pronouncements) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Current assets	$ 1,889,454	$ 1,883,508	$ 1,879,850
Total assets	5,113,367	5,052,884	5,032,985
Current liabilities	715,666	744,937	744,102
Total liabilities	$ 4,631,890	4,657,551	4,650,436
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Current assets			1,879,850
Total assets			5,032,985
Current liabilities			744,102
Total liabilities			$ 4,650,436
Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Current assets		3,658
Total assets		19,899
Current liabilities		835
Total liabilities		$ 7,115