Supplemental Consolidated Balance Sheet Information (Schedule of Prepaid Expenses and Other Current Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Prepaid expenses	$ 25,418	$ 20,436
Derivative financial instruments	339	30,340
Insurance recoveries	0	19,884
Other	6,253	5,947
Total Prepaid and Other Current Assets	$ 32,010	$ 76,607