Long-Term Debt And Other Long-Term Liabilities (Other Long-Term Liabilities) (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Dec. 31, 2013
Debt Disclosure [Abstract]
Asset retirement obligation (ARO) liability	$ 96,368	$ 100,567	$ 120,591	$ 133,657
Capital lease obligations	24,188	25,876
Workers' compensation	17,681	17,997
Separation benefit plans	11,368	11,276
Deferred compensation plan	4,406	4,055
Gas balancing liability	3,623	3,623
Other	410	410
Other liabilities	158,044	163,804
Less current portion	16,891	15,019
Total other long-term liabilities	$ 141,153	$ 148,785