Contingencies And Contractual Commitments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Transportation and Storage Contracts, Fiscal Year Maturity
Next Twelve Months	$ 148,716
Year Two	132,547
Year Three	119,639
Year Four	107,400
Year Five	102,884
Thereafter	857,454
Total	1,468,640
Transportation and storage costs	140,500	$ 135,100	$ 137,700
Receivables, Long-term Contracts or Programs	26,000
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	$ 20,000