Long-Term Debt And Other Long-Term Liabilities (Other Long-Term Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013	Dec. 31, 2012
Debt Disclosure [Abstract]
Asset retirement obligation (ARO) liability	$ 119,900	$ 133,657	$ 135,592	$ 146,159
Workers' compensation	19,679	20,041
Separation benefit plans	9,871	9,382
Gas balancing liability	3,775	3,775
Deferred compensation plan	3,858	3,589
Other liabilities	157,083	170,444
Less current portion	11,629	12,113
Total other long-term liabilities	$ 145,454	$ 158,331