Long-Term Debt And Other Long-Term Liabilities (Other Long-Term Liabilities) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2013
Debt Disclosure [Abstract]
Asset retirement obligation (ARO) liability	$ 94,608	$ 100,567	$ 96,679	$ 133,657
Capital lease obligations	23,332	25,876
Workers' compensation	16,800	17,997
Separation benefit plans	10,560	11,276
Deferred compensation plan	4,454	4,055
Gas balancing liability	3,623	3,623
Other	410	410
Other liabilities	153,787	163,804
Less current portion	16,806	15,019
Total other long-term liabilities	$ 136,981	$ 148,785