Long-Term Debt And Other Long-Term Liabilities (Other Long-Term Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Long-term debt and other long-term liabilites [Abstract]
ARO liability	$ 70,170	$ 98,297	$ 100,567
Capital lease obligations	18,918	22,466
Workers' compensation	15,163	16,551
Separation benefit plans	4,943	9,886
Deferred compensation plan	4,578	4,244
Gas balancing liability	3,789	5,047
Other	410	410
Other liabilities	117,971	156,901
Less current portion	14,907	16,560
Total other long-term liabilities	$ 103,064	$ 140,341